Research this area:

I think Captain Samuel O. Mossah Sewer, Sr. was a out of wedlock child, but his father may have been "Phillip Martin Sewer". Captain Samuel O. was the father of Samuel O. Jr. Sewer, who was Louise E. Roberts Sewer husband. Irvin Sewer one of possible 6 children of Louise.

Your mystery connection may lead you toward Captain Samuel O. Sewer mother, may be the Frederiksen connection.

Remember Phillip Martin Sewer had 5-6 children. Check:
Birth certificate , baptisimal record book, census records for Captain Samuel O. Mossah sewer, Sr. (mother/father), (your linkage maybe there).

I have some family trees of both sewer families. But are still being worked on. On the Robert side; George, Geraldine, Roberts, Hennessey.

Good luck!