Does grandpa pronounce "gigi" or "gijia" in Japanese?

In Japanese, people usually use "ぉさん" when addressing their grandfathers face to face or talking about other people's grandfathers.

But when you say your grandpa outside, you should use "grandpa" (search). If you have a good relationship with grandpa, you can call it "grandpa" (Ogilvy-Ogilvy-that's what you call Jijia)

"Gigi" (that is, Gigi as you say) has no sense of respect, just like the "old man" we say.