Dear Sudhir,
Husband of ur sister has not right, in any manner, to claim the share in property of ur parents, whether ur sister is interested in property or not. Its only ur sister who can claim right in property of her parents.
As u mentioned that husband of ur sister has already filed a case for claiming share in property, firstly check whether he has filed the case on his own name or in the name of ur sister. If he has filed the suit on his own name then court will dismiss his case.
The other way to stop him is that all u siblings file a Suit for declaration in the COurt and claim ur share in the property. Any brother or sister can relinquish the his/her share in favour of remaining siblings.
you can contact me at saagar_bhatia@hotmail.com or on 09810262582 for any further legal advise.