1.Neither declaratory suit nor succession certificate is required to make your mother sole owner of the proeprty which appears to be an immoveable property.
2.Make a deed of gift in favour of your mother transferring your respective 1/8th share to make her absolute owner of the proeprty.
3.the said deed of gift is to be registered on payment of stamp duty though.
Forget the suit.It is not the solution.