Well this definitely warrants a sit-down, with A and I think with B just so you know where both of those guys stand. Think a lot about what your feelings are too, and where you would like this to go (depending on how the guys feel).
There is a potential poly relationship here, but first everyone needs to get their true feelings on the table, and clear up any confusion. Emm and Marcus are both right in their posts too.
I hope things go really well for you; I am keeping my fingers crossed.
Love means never having to say, "Put down that meat cleaver!"