Robert & Johnny: We Belong Together
Johnnie & Joe: Over the Mountain, Cross the Sea
[purchase]
Both of these come from the Doo Wop Box, a box set my wife picked up at the library a couple months ago which has given us a ton of great doo wop ditties we never would have brought into our collection otherwise. I don't know anything about either of these duos, other than that they fit the theme and they're good songs!