Can a mother get custody if she was married and after 10 years shows she had an affair and the child isn't yours?

In custody cases, the primary focus is on the best interests of the child, rather than the parents' marital history. If a mother had an affair and the child is not biologically hers or her husband's, the court will consider various factors, including the child's relationship with both parents, stability, and the ability to provide a nurturing environment. If the mother can demonstrate that she has been a primary caregiver and can continue to provide a loving home, she may still be awarded custody despite the affair. Ultimately, the decision will depend on the specific circumstances of the case and the laws in the relevant jurisdiction.