Ha! I twisted both ankles a few times, then I broke my left ankle when it folded over as I jumped to catch a ball and landed off-balance. Yes, there could be something 'structurally' wrong with your ankle that may have needed correction when you were a child, but if you're at or past puberty now its a little too late for a minor correction. Eventually, the joint will wear and correct itself, but it can leave the ankle a bit unstable. As already been noted, once you really wrench a joint good the ligaments and tendons get stretched and never really go back, so instability is always a higher risk.
The only thing I can recommend is to see a sports medicine specialist and ask about exercises that you can do to strengthen the ankle, wear supportive shoes (mid or high tops) and consider a sports wrap.
On edit, I should note that today my left ankle (the one I fractured) is so unstable from multiple strains that I can just be standing still some times and it will fold over when I switch my weight from one foot to the other. FUN!