Can you identify the relationships of the performers of these clips, i.e. brothers, sisters etc.

And can you spot the performer/band that sounds like it is but it’s NOT related?

Including The Bee Gees,Sister Sledge,Scissor Sisters,Right Said Fred,Oasis,The Nolans,Nat King Cole and Natalie Cole,Jedward,Frank and Nancy Sinatra, The Carpenters