Don't worry about nit crying, you'll cry alot at the funeral (NOT trying to be funny).
Why did you G. Granny take care of your brother like a mother? Did your mom hate him?
Anyway, I'm sorry, I never knew my dads parents, and my moms couldn't speak english so they were more of an acuantince more than a grand mother to me and my great grandparents never knew me, so honestly I can't say "I know that feel".