I have 3 daughters. My oldest (stepdaughter) is 46 and never wanted kids and doesn't have a partner. My middle daughter is 40 and seems to be on the fence if you bring it up. But at 40 I doubt it will happen and that's okay. I always told them not to have kids for me do it for yourself if you want to.
My youngest daughter always wanted kids. She's 37 now. It took her awhile to find the right guy and convince him to get married. They were actually waiting for him to finish school...he's a PA. Then we knew she'd likely have fertility problems and indeed it took a long time to get pregnant. This may end up being the only grandchild, but that's okay, too. We'll smother this one with love.
Having grandsons is nice, too. They probably just aren't as much fun to knit for.