I am thinking of marrying someone that still financially support his ex wife and her child (of which is not biologically my ex's child). My ex was only married to this woman for 2yrs. and they dated for 1yr. before marrying. My ex has been in the child's life for 3-4yrs max, yet he pays child support to her mother just as if the kid was his. He pays half of all of the child's expenses HOWEVER, he can't claim any of this money on his taxes because he never adopted the child, never changed her name to his. He also has both the ex wife and child on his health insurance and says that he's willing to take the ex-wife off, but not the child. He lives in a different city as the child but still picks the child up for weekend visits, buys her things, clothes, electronic gifts, etc.

Despite his ex-wife having a new boyfriend, my boyfriend is STILL paying the car note on the ex-wife's car and claims that she sends him checks that cover those payments and he says he is not willing to change this agreement because her credit is too bad to get the car refinanced in her name. My question to him is, why can't she just send the checks directly to the bank?
He also pays the car insurance for this car and claims that the ex is sending checks to him to pay him back for these payments as well. Again, why not have her get her own insurance policy and pay the bill herself?

To add, he still has a very close relationship with his in laws and said he'll forever call them mom and dad regardless of who he wed's in the future. He confides in the ex-father in law about his personal affairs and I feel this would cause a problem for our household if I were to marry him, because they would keep their daughter updated on what is going on in our home.

He called IRS and was told that he has no legal write to claim her on his taxes unless the mother agrees to it, and that while his actions are noble...he doesn't get any kind of tax credit either. He pays close to $6,000/yr in taxes and needs every credit that he can get, so this is why I have a problem with the ex-wife not allowing him to either alternate years claiming the child or her giving him a portion of her return (which he claims she can't afford to do).

I have not and don't plan on encouraging him to totally abandon this child. I feel that it would be fair to 1. end the overnight stays at his new home, but allow her to visit otherwise as long as "WE" both agree on when she comes; 2. come to a definitive dollar amount that he will contribute to her mother (his ex-wife) and stick to that amount. I suggested that he agree to help buy her school clothes once a year and give gifts on special occasions, but not a monthly amount. The child's biological father is incarcerated.

There are other issues that we don't agree upon, but they don't have to do with step children or the like.

I am here to either confirm what I am planning to do, which is to break things off with this guy because he is too involved with his past (his ex-wife). I also don't like the idea of financially paying for a child that he's only known for a few years himself. I know what I want out of life and I realize the a relationship may not come in the way that I'd like, but it just seems that he's not being wise not to have any legal binds to this child and it overwhelms me that he still pays her expenses (even if it is just the car note and the insurance).

Am I being a total (curse word) not to want to continue our relationship and being unreasonable?