Where common law marriages are recognized as legal, they must end in the death of one spouse or by divorce, just like traditional marriages. You must file a complaint or petition for divorce, and children born to the union are legitimate. Therefore, custody is decided in exactly the same way as if you were dissolving a traditional marriage.
Best Interests of the Child
Courts determine custody based on what is in the best interests of the children, and state laws typically cite a list of best interest factors that a judge must consider. They include issues such as the child's wishes if he's old enough, as well as which parent was the child's primary caregiver when the marriage was intact, and incidents of domestic violence. Based on these and other factors, the judge determines which parent should have primary custody post-divorce. Until the court makes a ruling, both common-law parents have an equal right to custody. This is in contrast to the rights of unmarried parents, where the father typically has no rights until the court establishes his paternity.