Bob Hitchens was a Muggle who married the witch Isla Black. Their marriage caused her to be struck off the Black Family tree[1].
Behind the scenes
- It is possible that Hitchens was in fact a Muggle-born wizard. Although the partial family tree lists him as a Muggle, it does the same for Muggle-born wizard Ted Tonks, possibly indicating that the Blacks didn't draw a distinction between Muggles and Muggle-borns.