I'm not currently in a relationship, but have been in 3, and have been in love with all three (1st Liz, with whom i update on my life yearly, 2nd Amanda, with whom i still deeply care for, and 3rd Steph, who is currently my closest friend). The thing about love is that if you love someone for who they are, then you'll always love them. Most people nowadays love someone for who they can be for them (ex. a man loves a girl because that girl is a very potential canidate for being his life long wife). But then when that girl is no longer the life-long wife he thought she would be, then he wants a divorce (he didnt love her for who she was, only for what he thought she could be for him). I feel this is a big reason for why there are so many divorces these days.
Me, i loved my gf's for who they were, and they are still the same people. Therefore, i will always love them, but am no longer 'in love' with them. I want what is best for them, and i know that i am not. I know that none of them are my soul-mates and vice versa, so it makes no sense for me to try to pursue such a relationship any more. Being that i'm not their soul mate, i'm not good enough for them, and vice versa.
If i was in your beau's situation, i would want you to share with me your concerns and worries. After all, if we wanted to have a healthy marriage, open communication between us would have to be a must. But i would not give up loving those girls of my past. It would be important for my to-be wife to not only trust me, but understand that this is a part of who i am. If she can't accept that part of me, then she doesnt accept me as a whole.
This is of course one single view, and i do believe i'm not a common person so my view may not apply. I still hope it helps tho!