Say,aren't you kin to...?

[marv2]

Motown's very own Emotions, The Three Ounces Of Love, were all sisters! And Lovesmith were a quartet of brothers I believe.

Of course, Gladys Knight was related to most of her original Pips: brother Bubba Knight, sister Brenda Knight, and cousins William and Eleanor Guest.

Ok, so if were going to go with the obvious then:

the Jackson Five
the Osmond Brothers
Sister Sledge
the Pointer Sisters

I don't think this is what Arr&Bee meant however.