What other permutations of BB songwriting collaboration don't exist? Pretty sure there was never a C. Wilson/M. Love, for instance - All This Is That (Wilson/Love/Jardine) being the closest I can think of. For that matter, I can't think of a B. Wilson/D. Wilson off the top of my head either.
Apparently "Don't Let Me Go" from the 1974 Caribou sessions is a Carl and Mike collaboration, it'd be interesting to hear that one!