What I've gleaned from it is that Henrietta Rew married Will. Whiston 1781 Cov. but had no children.
She had at least one sibling, Skears Rew who married Jenny Bradnick 1791 Cov. who appears to have had an illegitimate daughter Henrietta Turner who is mentioned as a natural child rather than a daughter.
Niece Sarah Wilson Westley nee Rew m. 1808 Cov. had 7 surviving children (possibly I other John b. 1810) Mark Malin, William Whiston, Skears Rew, Henrietta, Thomas, Mary Ann & Sarah.
2 other niece's are Ann Phipps & Sarah Walker who was at the time living with her son John ?
The other beneficiary was Henrietta's husband's son by a previous relationship William Whiston Batt/Bart who's living with his father-in-law a Doctor Jordan.
Is this what you have?
According to IGI Henrietta's other siblings were Benjamin, Sarah & Sally.