Will & Probate related query.When & how to present the will in FDPcase

My mothers elder sister has made a will in my mothers name.Now she has expired. Our case is still pending for Final decree. In original plaint it is decreed as 1/3 equal share between my mom,mom sister and mom brother. Now our advocate is not presenting the will in FDP case and he is telling that the witness should present the will. If we are not presenting the will,my moms sister name will be deleted from the suit. Proper guidance is not provided by our advocate.lf i ask we can make a probate of a will,he is telling its not required. Will which is made is registered and it is an open will. When and how to present the will in our FDP case? Is probate necessary? Kindly guide me and help me out. Thanks & Regards