Dean Thomas is a gryffindor student from the same year as Harry. His best friend is Seamus Finnegan.
He is a member the DA, the spell-breaking year and of the second Pride, and he is also the boyfriend of Lindsay Jordan.
He has always thought he was a muggleborn, though he didn't know his father. During the spell-breaking year, it was discovered he was a halfblood, and later on that his father was Regulus Black. This makes Dean Sirius' nephew, Meghan's cousin and a black by blood. This enables him and Kreacher to bond. He is also left-handed.