Travel restrictions

According to current U.S. policy you can visit Cuba to see immediate family once every three years.
According to current Cuban policy you can visit Cuba at any time for any reason unless they simply don’t feel like letting you in:

[Cuban] State Security impeded Elaine Pérez Rivas from entering Cuba and forced her to return to Miami this past 18th of May, because she is the daughter of the Lady in White Soledad Rivas and of Roberto de Miranda Hernández, prisoner of conscience from the group of 75, who is currently out on extra-penal license (a form of conditional parole).
Elaine has not seen her family in 11 years, the event has affected the health of her parents, who accuse the government of being scammers because the Cuban interests section in Washington had given her a visa to travel to Cuba.