It’s mostly genetic. However there are some exceptions now and again. I’ve known a few people who were short and then grew 6 inches in a summer. In my wife’s family people are either really short or really tall. She’s 5”8’ and her sister is 5 feet tall. She’s taller than brother her parents as well. Half her cousins are quite short and the other half are pretty tall. Genetics are weird. Just ride it out