As far as John & Frederick are concerned they could be grandchildren but using the GRO has failed to find them using the known ages and place of birth.
Alan
Searching the GRO can sometimes be tricky, with omissions, curious spellings, and no wildcards.
In the case of failure, I use FreeBMD to find "possible" records (complete with dodgy spelling) then use the FreeBMD details to find the GRO record (with the precious MMN).
(Even this doesn't always work)