My father is 47 and already a grandfather of 8 year-olds, isn't that young?

I (31 F) married for 10 years and our twins are 8 years old.

My father is my mother's exact age; just 4 days younger than mom. They're still together. They got married young when I was 3 years old. He's now 47 years old.

I still can't believe he was just 39 years old when he became a grandpa for the first time. Isn't that young? Then again he was very young when my parents had me; both were in HS. He still looks younger than his age. Wow.

My father is 47 and already a grandfather of 8 year-olds, isn't that young?
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