Your sister needs to hire an attorney. Family members need to help her with the money for a retainer. It is very hard to get sole custody. Florida does not even call it custody any more the parents have what is called a Parenting Plan that delineates what time the children are with which parent. Florida courts have been leaning more toward about 50/50 with regards to parenting time. Your sister will have to prove that the father is unfit to have normal standard parenting time with the children. That will require a lot of work. She really needs to hire an attorney. Good luck to her.
B. Elaine Jones, Esq.
I agree with my colleagues. If the children have an attorney ad litem or a guardian ad litem that is "leaning toward" the father, then your sister may have a real problem and you may not be privy to all of the information that the guardian ad litem or attorney ad litem is able to ascertain. I would strongly suggest that your sister obtain the best family law attorney that she can afford to represent her in this case. Best of luck.
This answer is for general informational purposes only and should not be relied upon for your particular case nor is it intended as legal advice. I have not reviewed your case nor have I met with you and the answer to this question does not in any manner whatsoever establish an attorney/client relationship.