Just been going back over my notes and checking against yours:
Benjamin Withers b1713 son of Joseph Withars, a butcher, married Sarah Wilks 1725 and then Elizabeth Guest 1747 followed by 3 children: Joseph (b c1728) Mary (b1753) and John (b1764).
I also have a Benjamin Withers born 1723 in Birmingham, parents Joseph Withars and Rachel Brown, married Sarah Wilks 1725 (no children), Mary Weston 1733 (four children) and Mary Hopkins 1772. There are two children John Withers born Dec 1772 and Richard born May 1774, but both of them have Sarah as their mother, not Mary.
Can't find much info of Mary Hopkins, and no children from Sarah Wilks with Benjamin.
grimace
David