Goodness, these are elusive aren't they!
I thought I would start with the less common name first but....
I do not see an English death for Robert Bernard KEEN at all. There
is a 1935 death for a John Bernard KEEN and I cannot help wondering if some confusion has arisen as a result. It's not him. he was only 8 years old.
in 1901 it looks as though this Robert is in London, a Hostler, Buck yard. born "Bucks ford Aylesbury"
He is lodging with George & Matilda Whitney, but Matilda also born Bucks ford Ayelsbury and is nee KEEN.
Looking at the family of Annie JOHNSON/BROWN and Robert Bernard KEEN it seems all children are registered under BROWN
I think this one is the youngest one, known as KEEN
BROWN Robert. 1904 D qtr, in Salford vol 08D page 129 MMN Johnson (ie not the Liverpool one the tree has linked. That one has a MMN of AUGHTON)
so is the 1906 marriage to Ellen WARD of Robert Bernard KEEN, the RBK b 1882, Northamptonshire? because surely if you are acknowledging a child as yours that was born in 1904 you wouldn't leave and marry someone else and then go back in time to have Frank KEEN mmn JOHNSON in the J qtr of 1909. (he died 1910)
(Although human beings are full of surprises

)