I'm not quite sure what you mean here.
It is unclear from your post whether he was called "A Samuel Brooks" - that is, he had a first name starting with an "A", as you have put it as a capital letter, and as capital letters are used for people's names, this suggests the "A" was his name.
Assuming he was actually called just 'Samuel Brooks', you say he was your grandad, so do you not know who your grandmother was?
Is this what you are trying to find out?
Do you know where and when your grandad was born?
Have you found him in the 1881 and 1891 Censuses?