Have solved the mystery. Lt.Robert Maynard died 1751 in Kent Co,England, leaving estate to 1. daughter-in-law Elizabeth Judson, with NO children or grandchildren mentioned 2. his brother Thomas' widow 3. his mother Ann Maynard 4.his friend Thomas Gee/Lee/See ? and 5. his two nephews Thomas and John Peck and niece Ann Peck [Rathbun], children of his sister Margaret Maynard [Peck] Mitchell.All of those named in #5 were living in Boston, MA, USA.
No children are mentioned at all, which suggests he had none living in 1750 when will was written. No grandchildren were mentioned, suggesting none living in 1750. Those desiring to prove descendency from his line will need to search further for definite proof.