1. Mere claim is not enough.
2. it is not clear how many papers does he have to support his claim.
3. The Patta would work in your favour.
4.This person even of some share would be from old devolution of property which is not so easy for him to lay his claim.
5. Now since you have bought the property without notice of this fact you are bona fide owner.
6. In that event continue your possession and let him run around court to prove his share.
7.If you have nothing to do for the time being.