After 79,000 neighborhood meetings, months of discussion, and an outpouring of more than 300,000 suggestions from citizens, Cubans will vote in a referendum Sunday that could redefine family rights — including legalizing same-sex marriage. The proposed new Family Code would be among the most progressive in Latin America, defying a long tradition of machismo in Cuba. In addition to approving same-sex marriage, it would allow gay couples to adopt, and increase the rights of women, the elderly and children.