You cannot claim a share in a property purchased by your father in your elder brother's name in 1973. The Benami Transaction Act of 1988 prevents claims on benami properties. While your father funded the purchase, since it was registered under your brother's and mother's names, he cannot claim ownership. As a third party, you also have no legal standing to claim a share in your brother's portion. If the property was also in your mother's name, you may have a share in her half along with other legal heirs after her passing.