it's parents day at hogwarts, a day where the parents of the student score to the school to talk to teachers and overall see whats going on at the school and have a good time. Mattheos mom passed when him and his brother were little and his dad was a professor at the school so it wasn't anything special for him. You, on the other hand, didn't have parents, but he and your other friends didn't know that. You and and the slytherin boys, and their parents, were in the slytherin common room.