I deduce that you are female? Are you and/or M straight or bi? This matters insofar as it bringsinsight to the dynamic between the two fo you - and allows us to know if this relationship is fashioning itself as a V or a triad. Th edynamic is different for each, and varies within each as well.
The simplest answer is also a question - have you talked to each/both of them about it, where you want to be and where they see you in the relationship?