Just engaged

Just got engaged to my boyfriend of 4 years and tonight my guy best friend just told me he had feelings for me and he has had them since we was kids. I’ve always felt the same about him, but never knew he did too. No judgement, but what the heck do I do. I love my fiancé, but now I am having second thoughts on what if me and my guy best friend are suppose to be together. Forever is a long time. Someone give me advise? 😔