When someone first gets sober, they say not to make any drastic life changes or big decisions for the first year. Or at least the first six months. Is he in a 12-step program or getting any kind of counseling about his sobriety and depression meds? If I were you I would gently let him know that it's unfair to give you an ultimatum and you won't accept that, and remind him that he just needs to work on himself, grieve the break-up, and not ask for or demand any big changes during early sobriety. As long as his needs are still being met in his relationship with you, your relationship with his brother has nothing to do with that and should not play a role in his happiness. His emotional well-being is not dependent upon outside sources (like you being monogamous on demand), but on how he manages himself.
Last edited by nycindie; 10-14-2013 at 05:54 AM.