Could Catherine Sarah be named after her two grandmother's?
Yes, I wondered that but I think Catherine might be too young to be John Jr's mother.
I tried to find their marriage but without success.
What does "F. S N"after Mary's name mean?
Don't forget ages on 1841 are rounded down, so Catherine could be almost 45
There's a burial of a Catherine Fryer in Aldersgate in November 1842. GRO has a death registration in Q4 1842 in East London for a Catherine Fryer aged
46 . This would suggest she was born c1795/6 and would have been about 20 when John Jr was born, which would be very possible
Added: found another record for the burial and it's the same Catherine - address Lauderdale Buildings. Age 45