It’s abduction, not kidnapping, when the non-custodial parent takes away the child. If it’s the custodial parent it’s fine.

whether a child is somebody’s daughter or son doesn’t depend on whether the parents are married. both parents have rights to be with their child unless a judge says otherwise.

Yes it is. Some courts even put it in the custody paperwork that one parent can’t take the child out of state without the other person’s permission. Look at it from the father’s side. How would you feel if he took your child out of the country without telling you. You’d be mad. Remember that the child is also his, regardless if you are married or not.

It is intereference with custodial rights. DNA makes it your child particularly if you were supporting it.