This doesn't need to be said because you are all MORE than aware of it... I don't know much about today's music. No matter... with that said...
Do they still have Duet groups? Ala Hall and Oates? The Everly Bros? Sonny and Cher? And note: Not referring to 'team-ups' for a song or two.. I mean as a going group.
Or Trios? The Pointer Sisters, the Bee Gees, Destiny's Child?
I'm not even going to ask about groups larger than than that.. they are DEAD.. The Temptations, The Ink Spots, The Lennon Sisters (and boy are you OLD if you know them).
I'm not aware of any which is NOT to say there are none... my guess is that there must be... I just don't know them.