I need advice :((

Basically I think I’m catching feelings for my friends ex🙄 here’s some background to the story. I’ve known him four years now and when I first met him I really fancied him and I told my friend K about liking him. Well long story short my friend gets with him and I don’t say anything to start a fight cause she’s my best friend, I just act cool and give them advice when they need it and I would tell him what to buy her for her bday and for Christmas. Anyways, I end up moving on. They broke up after a year and she’s had 2 boyfriends since and is currently with someone new. Fast forward to now, It’s been 2 years since they broke up and me and her are nowhere near as close. We were best friends but now we barely see each other. I just feel like I’m breaking the girl code if I go there with him, even though she probably wouldn’t mind I just feel so bad about it. Of all people I could catch feelings for ugh. What should I do? Should I just be friends with him or see if it goes anywhere ??