After Finn returned home from his first year at Hogwarts, all he talked about was Justin, his best friend who was sorted into Ravenclaw. Finn was so excited about him and told Patrick, Brody and Liam all the adventures the two had at school. Patrick immediately knew that his Ravenclaw best friend would be just as kind and sweet as Finn or else his stepbrother didn't want anything to do with him.
All these stories made Patrick excited to meet him which happened when he finally arrived at Hogwarts during his first year. Finn immediately introduced Patrick and Brody to Justin in the Great Hall. Patrick admired the traits that Justin possessed and found him a nice person to be around. He never made fun of anyone and he's always so sweet and caring to people he holds dear. Being Finn's best friend, this automatically made Justin part of the Dunbar and Hudson families and he occasionally comes over to their house during the holidays to celebrate and relax.
Same with Quinn, Justin is also a Ravenclaw and is one year higher than he is, so Patrick doesn't talk a lot to Justin in Hogwarts as they both have different things and places to attend to. When he does come across him, they smile and wave to each other in a greeting.