Might be tropeable. When a character is told they have a Secret Legacy, are secretly royalty, or otherwise inherited something from family. Nine times out of ten, it's from the father's side. Even when the protagonist is a daughter.

This came to mind from watching the BBC miniseries Jekyll, where it's part of a one two punch reveal. Everyone assumes that since Dr. Jekyll had no descendants, Jack is a clone. When it's revealed that he is a descendant via Mr. Hyde sleeping around in 1800's Scotland, the connection is through his mom, not his dad.