Hi..I know its a long time since you posted your message but did you ever manage to find anything out about your mum in laws birth mum? It just that I try to help people find their birth families & wondered if I can help...if you already found out let me know..ok..its just tha I looked up births for Joyce Hewings and if she was your mum in laws birt mum she would have only been 12 1/2 when she had her...thats the only Joyce Hewings in the births...Mary