This phrase has a very similar meaning as the phrase brother from another mother except not quite as familiar. The phrase is used mostly to describe close friends. It pokes a little fun at your buddies while at the same time conveying friendship and kinship. If the guys are life-long friends, use "brother from another mother" but if they're close buddies or you just want to joke around, use "bama from another gramma". You have to say it like it rhymes.