Boomers are 1946-1964. Definitely the older in the generation are in the great grandparent years, especially if they and their kids had kids young, but the younger boomers, especially if they and their kids had their first kids later, will be grandparents.
And that's still just for the youngest of that generation, not the whole of it... I don't know about you, but I'd hardly call a minority of a minority "prime".