Last fall, I had the awesome experience of rafting down the Colorado River through the Grand Canyon with a guided group. A few other people on the trip were my age (20s-30s), but the majority were middle-aged married couples, probably in their 50s. They were older, but most were not yet retired.
As everyone got to know each other, we realized that only ONE of the older couples had any children, and they only had one (now adult) daughter. All the others were intentionally, and happily, child-free. One man phrased it in a way that stuck with me, because it's exactly how I feel: "I just never pictured myself as having children. I simply didn't ever imagine that being part of my life."
All of these older people were exceptionally healthy, happy, and had spent a life's worth of vacations traveling the world and having amazing adventures. They were more enthusiastic and ready to try new things than any people their age I'd ever met. I'm sure that being child-free was a huge part of their freedom, their sense of adventure, and their enjoyment of life.
It showed me that being child-free isn't going to leave me shriveled and lonely and unfulfilled when I get older, like my relatives insist. It's going to give me the opportunity to see the world, to cultivate amazing adult friendships, and to do things people with kids could never do.