18 and Bulma is not realistic. It makes no sence for them to accept being in a Harem. Their personalities are to Strong for that.
The Kai no idea but You can make it work. The others are Sayains and probably Will be with him just because he is Strong. They are that simple.
So just goku twin with looks. Kinda meh. I get be8ng goku black and sense name bit something could change with looks..he just a copy of goku. Which is lame af for mc looks