I have raised my 10 yr old step son since he was 5 months old I have also raised my husbands sisters kids since they were 3 months and 13 months old I have had all 3 children for 10 yrs my husband has walked out on us 3 times in the last 5 yrs he has left all
3 children including his bio son each time he has met a girlfriend and after knowing her 10 days moved in with her he now along with his sister are trying to take the children away from me.what can I do

Get an attorney. But this is going to be an up hill battle. You actually have no legal standing to be taking care of any of the three children. Without that you have no right to keep the children at all.

OMG! I'm so sorry to hear this! I agree with the "uphill battle" assessment. I, too, faced the same issue when my ex-wife filed for divorce in 2000. We had been married 9 years at that point and I had been a father to her biological son who was a few months old at the time of our marriage. I made a major mistake in that I never legally adopted him. So, once she filed for divorce, she cut all ties off and sent him to live with his grandmother in another state until everything boiled over. After undergoing a full-blown Child Custody Evaluation (we have 4 biological children), I received primary physical custody of the 4 children, but the court's hands were tied with all matters concerning him. By then, my ex had pursued his biological father who, prior to then, had zero contact with the child. It was a court nightmare. The judge very sternly told her if she was "any kind of mother with a heart" she would see to it he spent significant time with "his father" - and the Judge very kindly looked at me and said, "I'm very sorry, Sir. I agree with you that he is your son, but there is very little a court can do in this matter." I didn't seen him again after that until he was 18 1/2 - he now comes to visit me as often as he is able as we live in different cities. The sad part is he spent very little time also with his brothers and sisters who remained in my care - but, reunions are awesome and they enjoy his visits as well.

All hope is not lost though, seek legal counsel - who knows what a great attorney and moral judge may swing - children are always worth the battle! I wish you the best!