First loves are just that - an unrepeatable experience. You will experience the same feeling over the person with whom you have your first sexual experience, there is a bond there, by virtue of the experience you shared.
But this has to be seen in context.
It is easy to be curious about what could have been, and tempting to try and find out, but that path is strewn with problems.
People move on and grow, even if, as in the case of your first boyfriend, other relationships may not have occured.
In your case, you owe it to your current partner to keep this curiosity in perspective - shared experience is not necessarily the foundation of a relationship - even a platonic one.
If your first boyfriend has not moved on in life, he may be kee to re-kindle things with you, which is fine, he has no ties. You however, should be very careful, because this could end badly for all concerned.
take a good look at your past relationship, and remember that that is what it is a past relationship - and going back very rarely works, so leave your feeling where it is - at vague curiosity level, and put your energy, intelect and emotion into your current relationship - which is where it will be best received.