Adult Siblings HATE each other

I am a 36 year old mother of 3, and am married to my best friend. My father was injured at work, and can no longer work, so we offered to get a bigger place (we were renting) so that we could help him out financially, only problem was that my 33 year old brother would have to come too, because he lives with my dad. We all agreed on what we could do to make it work, but the only one not keeping his end of the bargain is my brother!!! He is "handicapped" and lives off of social security, and can only pay so much, but has no problem racking up the expenses, and not contributing to anything. Put it this way, we pay $850 in rent not including utilities or food, or toiletries or anything and he pays a whopping $400 a month, while we pay the rest. Everything he says and does, he thinks he knows it all, when he doesnt know crap and tells my dad all kinds of lies, which he believes. My dad is definately on his side, and takes into consideration EVERYTHING he says, but when I tell him the truth, he already has it in his head that I am the one being difficult. It has gone to the extent that I am the reason we have fleas in the house, when it is CLEARLY my LAZY ASS brothers dog, and him not mowing the lawn, how the hell is it my fault?? It is just mY fault everytime something goes wrong. If I say something though my dad will want to leave and not be comfortable, and be homeless because he has no income, PLEASE HELP!

there needs to be some adjustment or compromise between the 3 of you,sit and find solutions or go to an expert coun,fighting will not solve anything,make this work by adjusting with each other and sharing the work,good luck