I don't believe the order is relevant; however, I personally say "Grandma and Grandpa."
Mary and Harry
Grandma- Grandmére Grandpa-Grandpére
Grandpa - "Dziadek"; Grandma - "Babcia".
In French, children say "grandpa" as "papi" and "grandma" as "mamie".
Given that grandma and grandpa are probably conceived as a unit, or partnership, rather than separately, I would favor the latter construction, grandma and grandpa's house. However, the other form would also be acceptable.
No. Grandpa refers to the male parent of your parent and grandma refers to the female parent
Grandma is "ะฑะฐะฑััั" (babusya) and grandpa is "ะดัะดััั" (didus).
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The antonym for grandma is typically grandson or granddaughter.
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A grandma is either your mother's mother or your father's mother.