No. He cannot obtain legal custody without a modification of the custody order by the court. He would need to petition for a change in custody. The court would review the petition and render its decision. It would be easier if your mother consents to the petition.
If you live in the US... The father's parents have no rights to custody at all. The father has the right to petition for custody, but he won't be given sole custody unless he can prove the mother unfit. He might, however, be given joint custody.
Guardianship, provided father does not have First Right of Refusal. Even without it, he can file a challenge for custody.
He can still file an injunction
If she has custody of the kids. Legal custody.
If the father has full custody, you can't do anything. If you have a custody agreement set up, that includes you having visitation -- take the father to court. If there is no agreement, take him to court, and get it settled. You failed to mention the jurisdiction where you live, marital status, whether there are any existing court orders, whether the father has legal custody and where the father got the authority to prevent you from seeing your child. You need to add details. See related question links.
If you have a custody order she will have to get permission from you and a judge to take the kids to live in another state. If you don't have a custody order, you need to get one. Make sure you are doing this for the right reasons - to continue to have a relationship with your child/ren. Not just to mess with the ex.
Not legally. Father can be charged with kidnapping.
Yes.
If they have sole legal custody- yes. If the parents have joint legal custody- each has a right to take part in that decision.If they have sole legal custody- yes. If the parents have joint legal custody- each has a right to take part in that decision.If they have sole legal custody- yes. If the parents have joint legal custody- each has a right to take part in that decision.If they have sole legal custody- yes. If the parents have joint legal custody- each has a right to take part in that decision.
Yes. see link
If the parents share custody there must be a custody order and visitation order. Those orders must be followed. Neither party has the right to make changes without a new court order.
Regardless of whether a parent pays support or not - the custody agreement determines who has rights. So if your child's father did not pay support but wants to see the child, and he has joint custody, he has every right, by law. This may not be morally right but it is legally right.