Welcome to our forum.
It sounds like things are in the very early stages for you, B, J, and L, and you will need to do quite a bit more communicating (the four of you together, whenever possible), before deciding what kind of a relationship you want with each other and how to handle things.
Polyamory.com will probably be a helpful resource for you; check out our various threads, and post any thoughts or questions you may have. A lot of support and collective wisdom here.
It's great to have you onboard.
Love means never having to say, "Put down that meat cleaver!"