Ravi, it is important to know which State's bonafide resident is your Son. This is important to identify his eligibility criteria. According to Tamilnadu MBBS Eligibility criteria mentioned in https://medicine.careers360.com/articles/tamil-nadu-mbbs-counselling , to claim Tamilnadu State domicile, your son:

1. Should be a bonafide resident of Tamilnadu
2. Complete 6th to 12th in Schools of Tamilnadu. In such case, he will be considered under Open Category.

But your son has studied only from 9th to 12th in Tamilnadu. So if he has to claim Tamilnadu's domicile, he should be a bonafide resident of Tamilnadu. On the other hand, if you look at Telangana eligibility criteria mentioned in our article: https://medicine.careers360.com/articles/telangana-mbbs-admission , to claim right to Telangana State Counselling, your son:

1. Should be a Local Candidate
2. Should complete his 12th in Telangana
3. If he is non local, he should have resided in Telangana for a period of 10 years.

Now we do not have much information about your son's bonafide resident status and local/non local status. So based on this information, please do take a call. To help you during admission and counselling, we have https://www.careers360.com/mbbs-companion.