Need clarification

earlier we have firm consisting of 4 partners(all own brothers) which is not in running currently. There is a property in the name of firm and partial of property was given to the partners' mother by all the 4 partners as gift and that was a registered gift(stamp paper also taken on firms name). Later the mother gave that property to one of the partner as will. These were took place long back around 25 years back Now that partner WHO GOT that property from his mother is going to sell the property. Now 2 partners filed case against that partner saying that gift given to mother is just adjustment/name sake and it's not valid and all the other partners will have equal right on that. So,could you please advise whether it is a valid gift or not and also please advise if there is any CASE STUDY to support us.