For FeMU it is usually Chrom. But when it isn't him it's either Owain or Lon'qu. The fangirls have no diversity.
For MaMU I see a lot more diversity. Lucina, Lissa, Cordelia, and Nowi are all common.
Other pairings I see are Chrom x Sumia, Lissa x Lon'qu,and Stahl x Sully