I started running when I was 9 years old, which was a 2 mile run home from school (we lived a little bit in the boonies). Plus, for the first year or two I thought it was only a mile, so I guess that improved my endurance.
I ran a lot in the woods, which also made it fun.
My dad started to run with me. He was 60 pounds overweight. The first time he made it about 100 yards before collapsing and almost having a heart attack. He rode a bike next to me and we would talk about stuff--father and son style.
Eventually he did learn to run. He never lost weight. But he could 7 miles with me and my brother, "Carrying 60 pounds of groceries," as he used to say. He also used to show up at our summer practices and run with my team once I got to high school (this was the middle 1970's). The coach liked having him around--a second adult to be out on the trails with us as a good influence, chapperone when necessary, and a second set of eyes to keep the coach informed on what was happening once we were out of sight deep in the woods.
My dad never lost weight because he probably didn't run regularly enough, and he's always had trouble with food, compulsive eating, stuff like that. He's thinking about what he'll eat for dinner while he's eating lunch, which is pathological when you think about it (he knows).
Anyway, a great thing for me was my dad talking to me (and my brother once he started coming along), either on the bike or running with us.
We never raced or went to a meet until high school. It wasn't about racing or being fast. I guess it was about our relationship and that running was fun in and of itself. My dad would say, "running gives me a sense of satisfaction I've never gotten from any other sport. You can really feel proud of yourself after running 5 miles." I don't think I understood that as a kid, but I sure remember him saying it and it got in my head somehow, and now that I'm an adult I know what he was talking about.
It's all about the fun. My dad also used to help us round up a few other kids, and we'd play tag and pom-pom (which is tag running back and forth with sideline boundaries), and we used to play soccer on the high school football field with no goalies--you had to kick it through the uprights to score a goal--which is harder than it sounds. We did a lot of running in many different ways. But it was always about the fun and my parents never put any pressure on us.