My uncle is demanding 25% of the property in gift deed

My uncle and his partner wanted to break their partnership in a shop 30years ago,my dad sold out his flat and gave away 50% of money to uncle's partner and could manage to give 30% only to uncle so uncle took 100% sole ownership of the shop and asked to give rest 20% once my dad arranges the money.My dad did all the transactions related to the shop and also managed to do business in the shop. All this while the shop was under uncle's name. My dad paid all the money last year but as soon as my dad died my uncle is asking for about 25% of the property now and he will handover the shop as a gift deed to my brother if we arrange the 25% in cash.We are not that wealthy to even arrange 5% of it.He is saying we cannot lodge a complaint we cannot sell out the shop and he will sell out the shop very soon as it's still in his name.All my dad's family members are not supporting us because they are going to get their share from Uncle to keep their mouth shut.My dad's 30 years efforts,money invested everything is going in vain. What should I do ?