Declaration of cancellation deed as Null and Void

Dear Sir, A tenant challenged my title and ownership based on a cancellation deed of my settlement deed by settlor. In fact I came to know of this cancellation only through the tenant. I got a copy of the cancellation deed. I filed a suit to declare the cancellation as null and void by designating this tenant as the only defendant. As advised by my lawyer, we gave paper publications to have any claim by any body and till date no claimers. The settlor expired in 1978 after almost 20 years from cancellation done. Settlement deed was unconditional and without any reservation to revoke and cancelled unilaterally. Under such ground we argued and Hon’le court, as prayed for, declared cancellation null and void with costs. The defendant has gone for appeal saying I should have filed suit against the successors of settlor as per Hindu Succession Act 1956 and could not file suit against third person like him and has raised question of law. Kindly advise and give some points and if possible please provide some SC / HC judgment references to suit this case. I am appearing as party in person and your advise will be very valuable. Thanks and regards, N.Mohan sai