Dick makes a good point about "the preoccupation of where a singer comes from".

I'd suggest that it is not a persons ethnicity or nationality which matters as much as their cultural influences. Example would be something like the reggae band UB40. Some might say that white boys singing reggae is somewhat plastic, but if these lads have grown up in close contact with the West-Indian population of Birmingham then surely this would be a cultural exposure which influences their musical education and choices.

Likewise, if someone has grown up around, or lived among immigrants from, example, Ireland, East Europe etc and has been in contact with the music (and culture)then I'd suggest the music and songs are as much a part of that person regardless of whether it is 'theirs' through ethnicity/nationality.