I just had this random thought I want to share while re-reading Chamber of Secrets.
So Colin Creevey is a muggle-born. He said so to Harry about his dad being a milkman and how they were both surprised when Colin got his acceptance letter. Then he gets attacked by the basilisk. With those facts, he is obviously a muggle-born, and we all probably know that.
But then, in Goblet of Fire, Colin is revealed to have a brother named Dennis who also got accepted into Hogwarts.
What are the chances of 2 muggle-born wizards in the same family???
I think it could have something to do with their mom, who (I’m pretty sure) was never mentioned, or it was a mistake/coincidence.