Fun thread.
Dad was active throughout his life and picked up running in the very first Kenneth Cooper-Bowerman running boom of the 1960s. He ran a little bit of track in high school, but was built more as a lineman. 6' 190 lb as an adult. I heard stories, never saw his times, but thinking mid 5:30s. He ran almost religiously for 15 years, 3X a week. Most of his runs were tempo level. He did about 35-36 min for 5 miles when he was about 50.
Mom claimed to be a star athlete as a youth. I'd say probably better than average. More of a gymnast's build, 5'2" and 110 as an adult.
Grandpa had a lean wiry build, which I seemed to inherit, somewhat. He 5'8" or 5'9" and in all the pictures he looked fairly slim, 130s - 140s. He was something of a gymnast in college. Other grandparents, I don't know, but that was a long time ago and they didn't do organized sports as far as I know.
My sibs were never that athletic. On is tall (6'4") tends to put on a lot of weight, and was never coordinated. The other is inherently lazy, dabbled a bit in swimming and little league and never liked running.
I ran 15s for 5K, my wife was a fast college mid-distance (4:30 1500) runner and our kids have got some mojo.