Character:Bob Hitchens

From UnknowableWiki

Bob Hitchens was a Muggle or Muggle-born wizard who married Isla Black. The marriage caused her to be burned from the Black Family Tree (BFT).

J.K. Rowling's notes for the tree indicate that Bob was a Muggle; however, the same is said for Ted Tonks who was in fact Muggle-born. It is possible that the Blacks simply did not distinguish between the two.