Bad forefather is recollected in family group? (5,2,1,7)
I believe the answer is:
birds of a feather
'in family group?' is the definition.
('birds of a feather flock together')
'bad forefather is recollected' is the wordplay.
'recollected' indicates anagramming the letters (letters recollected and rearranged).
'bad'+'forefather'+'is'='badforefatheris'
'badforefatheris' is an anagram of 'BIRDS OF A FEATHER'.
(Other definitions for birds of a feather that I've seen before include "A kind" , "they combine well!" , "people of similar character" , "Likes" , "like-minded people" .)