As a child Paddy had a strained relationship with both his parents. His father had a temper and emotionally abused him as a child. Paddy found his father after he committed suicide.
When Paddy Kirk first came to work as a locum for Zoe Tate at the vet surgery, he saw his time in Emmerdale as temporary. He was drawn to Mandy Dingle and they were smitten from first sight, but problems got in the way, including his mother. When she discovered her son was in love with a girl she felt was tarty, she was absolutely horrified. She offered Mandy money to marry someone else which she did, marrying her cousin, Butch Dingle. Paddy felt lonely and depressed. The following year, he took Bernice Blackstock to the Vet's Ball in an attempt to take his mind off Mandy but failed. He proposed marriage to Mandy that night, and she agreed. They married the following year but over the next two years, Mandy was away a lot. Her father needed a lot of care and she missed Paddy but began an affair with her father's carer, Neil.
A heartbroken Paddy became close to Emily Dingle, Butch's widow. They began dating, and on the day they were due to attend Marlon and Tricia's wedding, she got cold feet and Emily and Paddy stepped in to get married. Initially Paddy and Emily were blissfully happy and fostered children, including Debbie Jones. Unfortunately, over time, the marriage lost its passion. While Emily tried to make it work, Paddy was drawn into an affair with his wife's boss, Viv Windsor. The affair was revealed when Viv joked to Paddy over the phone that she had told Emily about their affair, and Paddy, who didn't realise Viv was joking, rushed home and confessed.
In the aftermath of the revelation, Paddy saw a very different side to his meek and mild wife. Throwing his belongings at him in The Woolpack, Emily announced her husband’s betrayal to the shocked audience and left. A mortified Paddy tried to keep a low profile, but after Emily left the village with Debbie's baby daughter Sarah, Paddy decided it was time he did something to improve his life. When Jo Stiles played a practical joke by pretending to be his Internet lover Fireblade, he went to Portugal for a rendezvous. However, he realised he’d been tricked and came back with brassy babe Toni Daggert. A horrified Jo thought Toni only wanted Paddy's money, and was relieved when Paddy and Toni revealed they were paying her back. Paddy later developed feelings for Toni but she told him she didn't feel the same way about him, so he moved on.
When Paddy found stray dog Titch, he started getting closer to Del Dingle – whom he persuaded to adopt the adorable pooch. The fun-loving pair started to fall in love, much to Toni's horror, who had realised she did love Paddy. Toni tried to split them up but eventually Paddy told Del that he still loved Toni. Sadly, their relationship ended when Toni discovered Paddy didn't want to marry her.
On 1 April 2008, Paddy's cousin Ross Kirk, hungover and driving to work with Paddy, accidentally hit a woman on a moped. Gennie Walker seemed fine and Ross, afraid of losing his job, convinced Paddy to say that he was the one behind the wheel. Genesis, or Gennie as she called herself, soon collapsed and went into intensive care. The next day, when Ross refused to come clean, Paddy went to the police station and told Shane Doyle what had really happened. Unfortunately for Paddy, Shane wanted a favour from Ross, which meant he had to keep Paddy quiet. Shane convinced Paddy he'd be sent to prison for perverting the course of justice if he came forward. Furious, Paddy stayed silent, but his relationship with Ross was strained as the year progressed. When he found out Ross was having an affair with Donna, he punched Ross and threw him out before convincing Donna to try and save her marriage.
Throughout 2008, Paddy began to fall for his receptionist, the mouthy Chas Dingle but couldn't work up the courage to tell her. At Christmas, he planned to give her a very expensive bracelet anonymously. Marlon wrote a note from Paddy to go with the box, but a mix-up occurred and the present went to Edna Birch. Chas, meanwhile, somehow got a roll of loo paper, which she lobbed at Paddy in anger.
In early 2009, when Chas and her rebellious teenage son Aaron left the Dingle home due to Aaron's behaviour, Paddy took them in, and even gave Aaron a job. Aaron began telling Paddy that Chas fancied him and he should ask her out on a date but then Aaron pulled the rug out and told him Chas would never want someone so pathetic or ugly. Aaron continued to wind Paddy up and sold some expired drugs when he thought Paddy was away. Around the same time as Paddy discovered Aaron's dealing, Marlon confessed that he'd kissed Chas the previous night. As Chas packed up to move back to the Dingle homestead with Aaron, Paddy finally plucked up the courage to tell her how he felt about her. She brushed him off, saying she didn't have time for this from him. The next day she asked if they could just be friends, and a hurt Paddy agreed. However, when Paddy saw Chas and Marlon being flirty at an event Marlon was catering, a drunk Paddy ruined the evening, destroying much of the food and trying to damage Marlon's reputation. Marlon and Paddy had a huge row, although within a few weeks they made up.
When Paddy told Chastity how special she was, Chas was so happy to have a man praise her that she impulsively kissed him. The next day, Paddy told her the kiss didn't have to mean anything, but Chas told him she cared for him and they spent the night together. They began dating, and soon Chas and Aaron moved back in to Paddy's home.
A recurring theme during Paddy's relationship with Chas was his insecurity about her feelings for him and his image. He tried to make himself over and to be more adventurous, especially as his 40th birthday neared. He wrote a poem for Chas, ending in a proposal, but decided to throw the poem away. Aaron fished the poem out of the bin and read it to everyone at Paddy's birthday party. A humiliated Paddy tore into Aaron for being so cruel after Paddy had done nothing but help him, and told Aaron he was nothing. The next day, both men apologised to each other for what they had done. Meanwhile, sensing that Chas didn't want to get married, Paddy convinced her he'd only been joking about the proposal.
In September 2009, Paddy and Carl King got in a heated discussion about Chas, and Carl revealed whilst Paddy was away one night he and Chas had slept together – whilst Paddy was still dating her. At first Paddy refused to believe Carl, thinking that he was just stirring things between them, and he knew Carl still held a torch for her. Upon realising he was telling the truth Paddy proceeded to finish his relationship with Chas – and throw her and her teenage tearaway son Aaron Livesy out of his home.
He later let Aaron move back in, and they created a special father-son bond. Paddy played a big part in Aaron coming to terms with his sexuality.
In 2010, Rhona Goskirk returned to the village of Emmerdale. She and Paddy's friend Marlon re-began a relationship, until Rhona expressed an interest in Paddy. She split up with Marlon, and began a relationship with Paddy. It was later revealed that Rhona was expecting Marlon's baby, while she was still with Paddy. Marlon was very upset and told Rhona he did not want to be the part of the baby's life. He refused to go to Rhona's first scan. On Monday 13 December 2010, it was also revealed that there is a possibility that Marlon and Rhona's baby may unfortunately suffer from Down's syndrome. It was later confirmed. On Monday 20 December 2010, Rhona decided she was going to go ahead with the pregnancy and Marlon and Paddy backed her up happily. The trio are all now good friends again. On Tuesday 1 February 2011, Marlon, Rhona and Paddy went for a scan of the baby, and this showed that its heart rate was healthy. In May 2011 Rhona gives birth to baby Leo.
In early 2012, Rhona started to make plans to propose to Paddy on 29 February. Unfortunately, Paddy got drunk and Rhona couldn't do it. It was up to Marlon to explain to Paddy what was going to happen. Paddy then discussed with Rhona the reasons not to get married and that it was a piece of paper and their love didn't need it. However, Paddy was wracked with guilt and made a T-Shirt for Baby Leo to wear saying "Mummy, Please will you marry Daddy Paddy". The plan was for Paddy to say Leo was hot and for Rhona to take off his jacket and see the shirt but Marlon took off the jacket and Paddy got angry, upsetting Rhona. Paddy then followed Rhona into the Ladies Bathroom in the Woolpack where he got down on one knee. Paddy and Rhona got engaged.
Paddy was offered a job in New Zealand and he and Rhona agreed to go. Marlon decided to go too, so he could be close to Leo, but he later changed his mind. Rhona told Marlon that she was still taking Leo to New Zealand. Rhona and Paddy marry, with Marlon arriving at the church at the last minute. During the reception, Marlon informed Rhona and Paddy that he had taken legal action against them taking Leo out of the country. After a lot of debate between Rhona and Laurel about taking Leo to New Zealand, Rhona took off with Leo. Paddy was forced to stay in the village after assaulting police officer. Later on Rhona and Leo make a reappearance in the village.
During December 2012, after everything had blown over, Rhona's college friend, Vanessa Woodfield, arrived and immediately got off on the wrong foot with Paddy. However after Paddy had been struck off from work, Vanessa, also a qualified vet, joined the surgery. She later agreed to have a share in the surgery and when Paddy was able to return to his duties he, Rhona and Vanessa all had their names above the door.
During May 2013, Rhona's life took a turn for the worse when she became addicted to the painkillers she was taking for her back ache. When she eventually ran out of the pills, her personality changed and she became aggressive towards Paddy and Vanessa. Rhona's dependence on drugs became increasingly worse and she started buying drugs from a dealer named Gary. Paddy and others were suspicious of Rhona's odd behaviour. He checked her phone and saw that she had been contacting Gary and lying about where she went. At one point he confronted her and grabbed for her phone. Rhona screamed and hit Paddy repeatedly before he demanded that she leave.
In July 2015, Paddy was furious when he heard that Robert Sugden, the husband of Chrissie, was two-timing with Aaron. He confronted Robert, but accidentally fell into a grain silo, which Robert chose to turn on. Thankfully, Paddy was saved, but was hospitalised. In September of that year, he met Leo's teaching assistant Tess Harris, and started an affair with her. Tess died in a car accident in February 2016, after which Paddy came clean to Rhona, who subsequently dumped him and began a relationship with Tess' widow Pierce. In October, he had another brush with death (this time alongside Rhona) when he crashed his Vauxhall Zafira in a pile-up caused by Emma Barton, but after being treated by the hospital, they both recovered and were discharged.
In April 2017, Rhona married Pierce; but almost instantly after the wedding, Pierce raped her. Paddy found out and supported Rhona, as did Marlon and Vanessa, and Paddy stormed into Pierce's office and punched him. He was chuffed when Pierce was found guilty.
- An inconsistency in Paddy's birthday occurs in Episode 2192 (15th April 1997), which sees him celebrating his birthday.
- "I have never snogged Marlon in this surgery" (to Vanessa, after catching her kissing Kirin in the vet's)