I think if you try not to sound like you're blaming them, they wouldn't see you as a bad guy.
You could tell them you are happy for them, but you feel lonely, and you would appreciate a bit more attention from them, either as a partner (your husband) or as friends. And that would feel a bit left out and you'd like their support.
I'm sure your husband also expected a quad with the four of you, I don't think there was any malice on his part. It's sad when things turn out like that, but you can't control your feelings. I agree you can control your actions, however, and they should be more careful and considerate towards you.
But they might be lost in NRE and not realise how you feel. Bring it up with your husband first, and then see if you can have a talk with everyone to let them know you want to work on your relationship with him more, and the other two relationships he now has might need to slow down as a result.