If he doesn't want nor see himself having kids with her but likes spending time with her, is supposedly ''in love'' (infatuated), calls her his girlfriend, likes going to the movies and doing other things but nothing serious... would that already be a friends with benefits by then?
A long-term, childless girlfriend he never sees a future him sounds more like a good friend to have unlimited sex with; there a friends with benefits. She would only be a girlfriend by verbal wording but what difference does it make by then?
Wouldn't she already become a friends with benefits?