Most likely not. If the mother had sole legal and physical custody and had the "step father" adopt the children without your knowledge - the adoption would be voidable. If he is illegally holding the children against your or their will, that is considered kidnapping in many states. Get the state involved.
If the biological father does not have have legal custody, then, no, he can't.
Generally, if married he has custody rights equal to the mother unless she has brought a petition for sole custody in his absence. If he is not married his custody rights must be established by a court order.
Yes and no. If the biological parent is proven unfit to care for they're children then the step parent has the right to APPLY for custody of his/her step children. Keep in mind that being married to the biological parent doesn't automatically make them the parent of the children nor does it make them they're legal guardian so there are no guarantees that the step parent will be given custody. If the children are happy with the step parent and no one in the biological parents family protest the application and the step parent is proven fit to care for the child(ren) then most usually the courts will award the step parent custody.
No, unless the baby's biological father relenquishes his parental rights, he would get custody of the child if the mother dies, not her husband. The biological father must sign his rights away to the mother's husband.
Nuclear family
The mother assumes automatic custody, unless she is unfit.
Being married or unmarried is not much of a determining factor when it comes to custody nowadays. In order to have custody changed you would need to prove that either your household and parenting abilities are substantially better than the other parent, or that their situation is detrimental to the children. Having a spouse does not necessarily mean that you are better able to care for the children, especially if the other parent has had custody for a significant length of time without the children having any problems in a single parent household.
You have to be established, legally, as her biological father so if you have not done that do that first. Have DNA tests done if needed. Then you can apply for custody or visitation rights.
Not without the permission of the child's biological mother. When a couple are not married and there is not a custodial order from the court, the law presumes that the mother has sole custody of the child in question.
yes, Vanna White was awarded custody of both children
see your other question
Unless the mother is unfit she will get the baby.