Get a good family law lawyer.
Information in the lnks below but also discuss with your lawyer.
If you live in the US... Only if her parents give her permission, or the grandmother has been awarded custody (the only way that will happen is if the parents are proven to be unfit, and it takes A LOT to prove unfitness).
tom is willing married.
Generally, in the United States, biological parents are always favored for custody even if the parents were not married. Unless the father is deemed unfit the court will favor him for full custody if he wants full custody.The court would require the father's consent to the appointment of the grandmother as legal guardian. If the father refuses to consent and requests custody then she must petition the probate court for guardianship. She must provide compelling evidence that the father is unfit and her guardianship would be in the best interest of the child. The court would appoint a guardian ad litem to study and evaluate the situation and report back to the judge. The grandmother must show that although she thinks the child would be better off living with her, she knows the child should have a good relationship with her father and she will do everything in her power to encourage that parent-child relationship. The judge would render a decision after hearing all the testimony and reviewing the report of the guardian ad litem. This is a serious situation and the grandmother mother should consult with an attorney who specializes in custody issues.
Only if she is unfit or willing. Otherwise the most he can get is shared custody.
Prove to the court that you are a more fit parent. Or have her give them back if she is willing. Other than that you are not getting them back.
If the current custodial parent is not willing to relinquish (or take), custody, then you have to retain an attorney and have it taken before a judge.
If neither of the child's parents are able or willing to care for the child in a safe, loving environment, the grandmother can petition the court for custody of the child. You will need to retain an attorney, and you will also have to provide proof that the parent(s) are not either willing or able to care and provide for the child. You can also petition for the court to award child support to be paid to you by one or both parents if you do become the legal guardian of the child, as well as requesting that they maintain medical insurance on the child.
No, but the father can stop the action from being done, plus it sounds like he should file for custody due to Parental Alienation Syndrome. see link
You cannot get married if you are already married. A church may be willing to bless your marriage.
Talking to his lawyer would be the best idea. You can then return to the judge and appeal that the order is not being followed, so perhaps custody should be changed (provided you can prove that you are responsible enough).
They do not wish to admit that they are married but willing to fool around.