Too much to handle?

Man I don't know what to do....I'm 25 newly married and right now living with my parents...I have a 26 year old brother and he just doesn't understand the actions he take is taken a told on our mom....my mama is stressing and getting depressed she says she is feeling like she will have a mental breakdown...if my mama leaves and can no longer take care of things that leaves me the oldest of all her kids...again I'm only 25....and newly married I just feel like everything is falling on me and I don't know what hat to do. I'm trying to make sure my husband is straight but on the other hand I can't just caring what's going on with my mom. If she can take care of things I will have to take guardianship of my youngest two siblings(16 year old and 8 year old) and I just wouldn't know how to try and displine a 16 year old the 8 year old respects me because I help my mom raise her....I don't wanna give up on my brother I'm just scared that this is gonna hurt not only me but my marriage.....I mean this has to be too much I don't know what to do.....