He is not popular but has had many relations with many girls.
He is not handsome or anything, but has had relationships with many girls.
「もてる」は Popular
「彼ってもてないキャラのはずなのに、なんだかんだ言っていろんな女性と関係を持ってるよね」を意訳して「彼は人気がないのに、沢山の女性と（肉体）関係を持っている」としました。
He is not popular but has had many relations with many girls.
二番目は、ハンサムでもなんでもないのに、というニュアンスです。
He is not handsome or anything, but has had many relationships with many girls.
日本 
