I'm 36 and he's 23 do we have too much age gap?

The guy I have a relationship atm is 13 years younger than me.
I don't care much but some friends called me a cougar and make jokes about it...
I know he goes with other girls too and I'm ok with it (I just want sex and time together from him) but I also wonder maybe we could try having a full blown relationship? We already date after all, and he does dating & romantic gestures for me... or it's better to keep it friends with benefits?
I'm 36 and he's 23 do we have too much age gap?
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