would any one be kind enough to explain why the two wives of my friends constantly having extra marital affair while he is a full man.?

Sex, fvcking, lust it's simple

They apparently desire something that they aren't getting at home.

Only the wives can explain that, honey. We don't know what their marriages are like (and neither do you). Maybe the wives are unhappy, maybe they are just sIuts who don't care about their marriage. It's not okay regardless of their excuse, but those women are the only ones who know why they're cheating.

Maybe it has nothing to do with his manhood but other things he is short in.

he may be inattentive to these women.. so the women seek someone else who will pay them attention.

Because they want to and what is a full man?

Basically, both must feel there is something they seek, want, or need that cannot be found with their spouses.

You misspelled "fool".

what do you mean full man?