The law was different for single mothers versus married mothers.
Which brings a whole other argument about whether she should be considered single since the marriage , if it took place, was not legal.
Why would it not be legal? The “marraige” he had in Kenya was a tribal ceremony and not a legal one. If I have a ceremony of a wedding and never turn in a marriage license application or get it formalized by the state, I am free to get married without divorce.