The best age to start orthodontic treatment is while the patient is still growing. If we start treatment early – at 8, for example – we widen the jaws and make it easier for the next teeth to come through in line, but starting at this age usually means we have to finish treatment once the child has replaced all their teeth, at around 11–12. That's a very long time, and it's normal for the patient to get tired of wearing appliances. That's why we only start early treatment if there's a situation in the mouth that we believe will interfere with the normal, natural growth of the jaws. If treatment is started at 10–11, for example, when all the baby teeth have been replaced by permanent ones but the jaws are still growing, the overall length of orthodontic treatment is shorter. It's important not to miss the growth period.
This answer is for general information. Your own case needs an examination by an orthodontist.