I am researching the Rossiter family tree and came across your postings.
I have Johannes Albertus Castein born 1901 in my database but he is married to Olive Frances Rossiter.She was born December 10th 1901 and was registered in the March quarter of 1902 at Hackey Registry Office, London.
They were married in Wandsworth, London in the December Qtr of 1927.
I have two children listed:-
Albert Frank Castein born 1928 in Wandsworth,London
John Castein (birth date unknown but probably after 1928)
If this matches with what you have and you have any information about Olive/Mary's parents I would be grateful if you would contact me please.
Hope this helps.
Have a good day.