ThirdWheel

I am married to a twin and I am ready to call it quits. Sigh. Here's the skinny. My fiance, i love her more than can be described in words, just proposed to her on Valentines. I would never leave her, and she has cheated on he once already. We have been with each other for 6 years but there is a hugh problem. Her twin sister is the most important person in her life. She has openly said it to me many times in the past and I am getting fed up with her sister. I have always busted my butt to get a better paying job or position to make our live lives easier. Her twin, whom I will Call M, and M's loser boyfriend are living in my house. M has been out of a job for 2 years. She says that she is actively searching for work but gets up a 3pm and fills out like 1-2 apps every month, if that. Her idiot bf conforms and just settles for only doing the bare minimum that he has to do. I am essentially paying up my own nose so that can stay. I just convinced my girl to quite her job because it was stressing her out. I told her "Babe, i make enough so that you don't have to work. Just worry about school and stuff and junk." My girl is willing to get a job to pay for her sister to stay at my house. She says that she wants to help her but that lazy ass M does nothing but play World Of Warcraft ALL DAY. I can't separate them, I've tried and my baby was balling her eyes out. I can't see her cry. I would rather stab my self before seeing my baby cry. I would go to the ends of the universe and back for her but after 6 years I can't take this any more. I don't know why she would talk to her about it. All M and her loser bf do is give excuses and validate EVERYTHING that they do and that tricks my girl into taking their side. She is a very sweet and shy person. I feel trapped. On one hand I don't want to lose or leave her but on the other I don't want to do this anymore.I've....even thought of suicide to escape...please help me