[He knows that, too. He knows it because his grandfather has made it abundantly clear, that they are important because they are family.]

Yeah. She's your daughter. And you have a son, too. They're twins. It sort of runs in the family, I guess.

[Billy looks down at his coffee, and then back up, eyebrows raised a little.]

You didn't know about us. It's complicated, really. We didn't even know about each other, for a long time. We were separated at birth.

[That's the easiest way to put this mess.]