Can third wife claim property if marriage wasn’t legal?

My aunt purchased a plot from TNHB and registered it in her name. After her death, leaving no children, my uncle married a woman in a temple (not legally registered). They separated without formal divorce. He later married a third woman, who was already married and only separated from her first husband. She had a daughter from her previous marriage. Before his death, my uncle transferred the Patta (title) and executed a settlement deed in favor of the third woman, calling her his wife. Can this third woman be considered his legal wife? Is the settlement deed valid? Can my aunt’s two brothers claim rights as legal heirs?