Question about a friend

So I have a guy friend and we've had sex a few times and we really got close to each other going on 3 years now...I was single when I first met him and he's really been a great friend to me...he even felt sry when I told him how my mom passed away and wanted to go to my mothers grave site with me...he also said things like I would make you my gf but I wouldn't be able to handle all the females and the attention he get because he's a singer which I told him I probably would be very jealous...he give me great advice since I'm in a relationship now but it seem like he watches my every move on ig and twitter...he has a gf and 3 kids but it always seem like we get closer to one another when we spend time with one another ....why does he give me advice and care about me so much if I'm in a relationship and if he's in one too?!!??