Hi Derrick,
My colleague and I are currently writing a book/pamphlet on the sisters, Edith and Ellen. From what we can figure out, none of the siblings had any children but they did stay close to extended family. When Susannah died (not long before Marcus) the family appear to leave Isleworth. Let me know if you'd like to know more. Would be interested to hear your angle on the family.
Best wishes
Caroline