Didn't know my grandparents very well. Dad never let us spend much time with them. Now that I'm older and moved away, I don't see my parents much either. With their health issues it's tough for them to get out, tougher for me to go visit (don't feel welcome). Don't have any kids of my own and I'm not sorry about it. My mom & dad always like to rub that in my face when I'm over there. Had plenty of female counterparts but none of them that I'd liked to have settled down with until recently, but we're both in our 40's and she can't have kids anyway.
I ain't lonely as long as I've got something to do; and as the old saying goes, the devil lives on an idle mind. I'm never idle...
Those of you who have kids and a good family--you don't know how fortunate you really are. Count your blessings and treasure them as often as possible.