Looks like we're probably cousins, I've just started searching this branch and here's what I assume
William and Esther (Laughton) Allen | William and Hannah (Harlow) Allen | and after that what I know for sure
Eliza (Allen) and Abram Trefethen | Arthur J and Bessie (Murray) Trefethen | Lyston A. and J. Winifred (Ellis) Trefethen | Norma (Trefethen) Karram
Eliza had a brother William H with wife Sarah and I know some about them. Recent census searches have made me quite sure about the other, though my mother always thought Eliza was born in Smithfield or Reidfield.