First thing I thought when I read the title. Me Mum's a Witch, Dad's a Muggle. Nasty shock when he found out. Don't know what made me think of him first.
Never really had a big role in any of the books, other than being Harry's dorm mate.
Then in the last book, Seamus is mentioned a little more often. His mother didn't want him associating with Harry. Why make this happen? I wondered what that was all about. Of the five Gryffindor boys in Harry's year, Seamus is the only half-blood. Harry, Ron, and Neville are full blood and Dean is Muggle born.
Sorcerers Stone-something Volemort wanted
Chamber of Secrets-something Volemort wanted opened
Prisoner of Azkaban-accused of aiding voldepoo, but was good
Goblet of Fire-transported Harry to Voldie
Order of the Phoenix-good group worked against Voldie