Prog stars who are related?

[Halmyre]

Scissor Sisters? A Pink Floyd tribute band is prog, surely...

[Toothyspook]

Guy Pratt is actor Mike Pratt's son.

Mike Pratt wrote, or co wrote, Little White Bull for Tommy Steele

(I guess only a few on here of a certain age may remamber that one)

[JKL2000]

Joseph Williams (Toto) brother Mark T Williams (World Trade) sons of John Williams (composer).

Porcaro's.
Paich's.

Yes, I consider Toto to be progressive!

So you can pretty easily connect John Williams to most prog:

John Williams > Mark T Williams > Billy Sherwood > Yes > Bill Bruford > almost anyone.