From LeakyPedia

Dean Thomas is a wizard in the same year as Harry Potter and in the same house: Gryffindor. He is very artistic and usually designs banners for Quidditch matches and for Gryffindor in general. His best friend is Seamus Finnigan.

[edit] Background

Dean doesn't know who his father is, as he left him when he was a baby, and so doesn't know if he is a half-blood or a Muggle-born wizard, and is therefore hunted down in Deathly Hallows. In truth, his father was a wizard who fought in the first war against You-Know-Who (Lord Voldemort) and left his family to protect them, never telling them that he was a wizard in the hope that it would keep them safe and well.^[1]

[edit] References

1. ↑ J. K. Rowling Official website, Section: Extra Stuff, Dean Thomas's background (Chamber of Secrets)