My question involves a child custody case from the State of: MA

We are in a real bind here. My soon to be step daughters are twins and one of the twins has an IQ of 78 (borderline) and is on an IEP in school. Her twin is of normal, maybe slightly above normal, intelligence. We have shared physical and legal custody of the girls with their mother.

To give background - we take the girls to all of their medical appointments (and pay all co-payments though she is responsible for medical bills and we for dental and vision), extra activities, etc as the mother is uninterested in doing so. We buy most of their clothes, gifts for friends' parties, etc. They spend nights at her house as my fiance is a chef and must leave by 5:30 am. We have the girls late on Mondays and Thursdays, overnight Saturday and alternate Fridays and they are with us every evening until she comes to pick them up after work (appx 6 pm). I will be moving in shortly and can adjust my work schedule so that I can take the girls to school every day (he picks them up daily). The girsls donot have a bedtime or structure at their mother's house. As long as she isn't "bothered" by them, she seems to be happy.

Here is the main problem - she neglects the girl who isn't as bright. She gets mad if she has to help her with her homework; she will not take the time to teach her basic living skills, etc. She actually wanted both girls in the exact same classes so the "smarter" twin could help the other with her homework so she wouldn't be bothered. This has been frustrating enough but now she is not feeding our not as bright twin breakfast because "she's slow in the morning" or oversleeps. In addition, after having been told repeatedly that the borderline girl does not like cheese on her sandwiches she keeps doing it and she has little to nothing to eat all day until she gets home with us in the afternoon!! The more intelligent twin "rules the roost" at mom's and bullies her sister a bit. I keep watching one of my girls withdraw so deep within herself, strike out at animals in anger, etc. because of this frustration, etc. The mother refused to attend the parents meeting for the sex ed class that our girls will be taking. The class is co-ed and taught by a male PE teacher that the girls just are not comfortable with. We were able to opt one girl out and when we raised the issue of the fact that both girls are uncomfortable with this teacher her response was "tough, they have to deal with teachers they don't like in life." This isn't a matter of liking or not liking- our 12 year old girls are not comfortable with a male health/sex ed teacher.

We have also recently found out that the mother was almost foreclosed on - again. Her spending is outrageous though little is on the girls. There is no child support paid by either party. They do not like having to go stay at their mom's and they absolutely adore both me and my fiance - and we are the strict ones.

We are both going nuts with worry for our girls and woudl like to pursue full custody. What are the chances of this? Seeing our girls like this is really getting to us.

Does this qualify as an unfit parent or neglect? To me it's horrendous but in today's world it seems as if anything goes.

Can anyone help? Give Advice?