Patrick and Theo officially met after the Hufflepuff - Slytherin Quidditch match in the second weekend of May 1993. That year, the only time he saw Theo was either during or after a Quidditch match or when he came across him in the Hogwarts castle.
It wasn't until the second term of third year that the two started to interact more. They greeted each other in the hallways and started to help each other in the classes they shared. It wasn't until long that the two started to fall into a romantic relationship. Theo confessed that he has always cared for him ever since he met him and that he couldn't help but feel something for him to which Patrick replied that he always thought he was handsome but that he never thought he would have a chance with him. Theo kissed him passionately in response.
At first the two had to keep their relationship a secret because Patrick feared how his family would react, but after seeing the positive response Finn gave to Brody when he came out as bisexual, they decided to lure Finn, Brody and Liam to an old classroom in which Patrick introduced Theo as his boyfriend. Ever since then, the couple has kissed and hold hands in public and they even go on dates to Hogsmeade together, where they buy each other nice things and have a drink together.
Theo is very protective of Patrick and will become hostile with everyone who has ever done him harm. If Theo finds out that you've done something to make Patrick sad or mad, then he'll get back at you. Theo will take revenge on that person because nobody messes with his boyfriend. Patrick secretly adores it when Theo gets so protective of him and gives him more kisses, which turn passionate really quickly. The two don't care what other people think of their relationship: they're happy and that's all what matters. Theo's rough personality compliments Patrick's soft one and they balance each other out.
Theo occassionally comes over to Hudbar Manor to celebrate the holidays with Patrick's family.