help me please

My husband is on child support with two of his kids from different women prior to our marriage. I provide the money for most bills due to him being laid off and he comes home with about 200 a month. With his first daughter who is 10 yrs. old we get her every weekend, every break, any time we want. I provide most financial support for her and we have her more than half the year . She only stays with her mom to go to school we provide for all her extracurricular activities, feed her because the mom is unable to feed her and her other 5 kids. Not including school clothes and supplies that we pay for with her. Along with throwing and paying for all birthday parties and extra stuff she wants. What is our rights with her? Is it possible to fight for custody of her?  On the other hand his youngest daughter who just turned 5 yrs. Old we only get her on weekends and provide for her when her mom allows her to come over on slim holidays. Who wants money handed to her as well as child support. When we ask for her she tells us no and she can do it on her own, then when she ready to hang out she then wants to just drop her off.  The youngest mother  has one child and two jobs where as my husband is doing side work. The mother has no time to share with her do we have any rights to fight for custody for her? I am a mother of three we rent our home and have two  cars. That I got and pay for and still have money to assist with the girls we have more than enough love, time, and money to take care of all five of our children. The father of mines is not