How to become limber ?

Ok my parents r Te exact opposite of limber and so am I. I want to do kickboxing (once I get a job since I'd have to pay for it myself) I'm a 16 year old girl and I'm woundering if it's genes or if u just have to train ur muscles, I try to stretch now and then but I just never see any improvement so I'm wondering if I'll ever get there.