Claim by second wife

Dear Sirs --- I bought a land in 2006 from Mr. Suresh. Mr. Suresh bought this land from Mr. Sukumar in 2004. Mr. Sukumar registered the document to Mr. Suresh though the document is originally on his father Mr. Narayan as he is passed away. Mr. Narayan have one son (Mr. Suresh) and three daughters. Three daughters have put the witness signature on the sale deed while registering to Mr. Suresh. I have received the Notices in 2008 from Mr. Sukumar second wife claiming she has a share on the property as the property is ancestor in nature. Mr. Sukumar have two daughters from his first marriage and one son from second marriage. The lower court gave the judgement to divide the property into 4 equal shares (equal shares to Mr. Sukumar and 3 daughters). From sukmars share of 1/4th, 4 equal parts to 1 to sukamr and 2 to 2 of his daughters from first marriage and 4th part to son from his second marriage. In essence 1/16th share to second marriage son. Now my question is I have purchased this property on my hard earned money and was not aware of all these family disputes. Please advise how to ensure my property is not partitioned. Mr sukamar clearly agreed in the registered sale deed that he will responsibility for any losses. How to fight my case in Legal courts?? Does the sisters have share even now even though they have put the witness signatures on the sale deed.