Hi Alison,
I cant help with what happened to him at this stage but this is Jims Birth Reg;
SINCLAIR Jim J C, December 1921, Richmond S, 2a 851
Mothers Maiden name BONGARTZ
Is that your Grannies Maiden Name?
John does not seem to have a Bongartz as his Mother

John W T SINCLAIR, December 1919, Lambeth, 1d 559
Mothers maiden name WEEDON
I cant find a Sinclair/Bongartz Marriage.
You need to buy your Fathers Birth Cert which will give all the details you need;
His Age, Occp etc + Mothers Maiden name etc.
Then when we know that we can find the Marriage and you buy that Cert to get both of their fathers names and occp etc. Hopefully then we can find Census entries fro them.
Trish
