Have you ever felt like this?

Lately I've been feeling like my time to have a baby is running out. I'm in my early 20s so that's not the concern. It's just that I worry that I don't know how much longer certain family members have on this earth, especially my grandparents, and I want them to be able to meet their first grandchild. Has this ever happened to you? If so, how did you deal with it? Or am I crazy?