Transfer of Property by will and adverse possession

I was given a property (agri land in Kanchipuram,TN) by my father in his unregistered will and he passed away in 2003. From 1997-2018, I was abroad and have not changed the title of the property. Now I have found that the property is occupied. I am planning to change the title of the property now. Documents of the property are in my fathers name, I have the original documents with me. The will is not contested, I have one sibling and we are on good terms. No dispute over passing of title by will. Will the current occupants of property have a claim by virtue of adverse possession laws? As per my understanding, for 12 years if the property owner does not make any claim, the ownership passes to those occupying. When does the 12 year period start, from the date of my father's death or date of transfer of title in my name? Also, if will is not affected, me & my sibling will inherit the property. Does adverse possession claim hinder a suit of possession on the basis of inheritance as well