Just kiss damn it. Also what happened between Minato and his bro?

I could be wrong but I believe his bro took away the women he lives

No I mean it doesn't seem like that.
It looks like Minato stole a kiss and by that time bro was already dating the Chick, so maybe in a rage he hit him or something.

In earlier chapters didn't he also catch them having sex ?

no ???? his older brother was already with her when he got interested