A baronet is not a peer, but it is a hereditary title, Mark Thatcher(Husband) was made one, Margaret Thatcher was made a baron (different, and is a peer) but he

A baronet is not a peer, but it is a hereditary title, Mark Thatcher(Husband) was made one, Margaret Thatcher was made a baron (different, and is a peer) but hers was a life peerage not a hereditary one.