Sonny and Connie were neighbors in their hometown Bensonhurst. They started dating in high school. They planned to run away together, but the night that they were supposed to go, Connie left Sonny. She didn't want to go because she wanted to live her own life in New York City. Sonny left and joined the mob. Connie changed her name to Kate Howard and went to Princeton University. She became editor and chief of the very popular magazine called, Couture.

Kate came to Port Charles to find a house "in the country". She walked into Sonny's office demanding to use his phone. At first, he didn't recognize her, but she recognized him instantly. She did not tell him they knew each other, she lied about her past to him when he asked. Finally he figured out who she was. Kate ended up moving in next door to Sonny, and despite getting on each others nerves, they slowly started to fall for each other again.

Kate ended up saving Morgan's life while he was drowning in her pond. In the process, she was bitten by a snake and Sonny rushed her to the hospital.

Later on, Kate was arrested for side swiping a cop's car and fleeing the scene. Sonny's lawyer, Diane was able to get her out on bail in Sonny's custody. Kate took the fender bender offense as a joke, deciding to go to Paris for a fashion show. Diane was able to get her community service instead of time in jail and as Sonny and Kate celebrated with a kiss, Ric walked in and told Kate that he was going to bring up the charges against her once again and make her pay by spending time in jail. Kate was then forced to terminate her relationship with Sonny.

Kate and Sonny talked, and decided to keep their friendship alive. They both wanted something more, but her ex-lover Trevor Lansing came to town and brought a mob war with him. Trevor had the hit and run charges against Kate dropped and delivered an ultimatum... she had to choose between Trevor or Sonny. She chose Sonny.

Another issue in the couple's relationship is Sonny's ex-wife Carly who does not approve of Kate and is jealous of her. Her and Kate do not get along and are constantly getting into arguments. Carly feels Kate is not "good enough" for Sonny.

At the black and white ball in November 2007, Kate and Sonny admitted that they loved each other very much. Sonny even took a bullet from Anthony Zacchara to save Kate's life.

In 2008, Sonny took Kate back to Bensonherst to where the first met. They went to dinner and the movies where they went on a date when they were teenagers. At the restaurant Kate and Sonny put quarters into a "psychic machine" and Sonny puts the card that came out into his pocket. After dinner Sonny and Kate go outside and he proposes to her. She tries to skirt around answering but Sonny firmly tells her if she's not going to say yes then don't bother saying no. Kate runs off and Sonny is left standing there hurt and pulls the card out of it which reads "You will stand alone." He then proceeds to buy the restaurant and movie theater him and Kate went to and burns them down. He goes missing for a bit and when Kate finds him again he is not so quick to forgive her for leaving him twice. He is so hurt that he inadvertently ends up sleeping with Claudia Zacchara, the enemy.