Best friend likes me

So one of my ex friends ex boyfriend and I have known each other for a very long time and we get along super well and we both consider ourselves best friends and say I love you and stuff and recently he told me he has a thing for me and I feel the same way but I don't know if I wanna ruin a friendship in case we don't work and the ex gf and I were really close for a very long time but then shit went really bad and now we don't talk but it makes me feel guilty, would it be a bad idea to try it out and date or should I just leave it as friends??