Not sure really - can always be lots of reasons really...depending on the family dynamics really

Are you somewhere near one of the main genealogy centres to be able to check more modern certs online - such as Glasgow or Edinburgh?
You know from this morning how we got to Phillip for a possible father for your grandmother. But, none of this info has been confirmed either with what we think is her birth cert in 1926 or her marriage etc.
It is always a stage at a time really. Without stressing the point, as as example, the Ralph name could come in as either a sibling to grandmother or an uncle to her etc

Would you believe, from the parent details for Fillipo, I have found parents' details back to Italy for his parents

Michele Valente born in Filignano on 30 Mar 1876 to Antonio Valente and Santa Coia. Michele married Marianna Izzi....and parents...
Marianna Izzi born in Filignano on 6 Mar 1872 to Francesco Izzi and Maria Cristina Faccenda. Marianna married Michele Valente...and parents...
But...all of this means nothing in genealogy without documentary evidence or some form of confimation

Monica