My brother and I may be a glitch in the algorithm of life here, but he is 6'6" and I am 6'1". Our parents are 5'7" & 5'5".
My folks made us work everyday hard and eat at specific times with rarely EVER seeing sweets aside from fruits. Read no candy or ice-cream.
We were swimmers,martial artists,hikers and the like.I raced BMX, he road raced 10 speeds.
We arose each morning at 5am and went to bed at 9pm.Exhausted.Lots of green vegetables etc. No fast foods. We had some lakeside land that we cleared and developed for a cabin during our growth period and were lifting heavy tree trunks and concrete blocks etc.
We are in our early 50's now and stronger than we were in our 20's with no health issues.
My parents are plagued with health issues , probably due to smoking and inactivity.
If genetics do play a role....we dodged that short ranged bullet whether activity played a role or not....who knows ?