In order to understand Castro's interest and loyalty to South Africa one needs to understand Cuba's struggle as well.

Calixto García, a general of Cuban rebel forces, (right) with American Brigadier General William Ludlow with Cuban rebels in the background, 1898.

The American Civil War, or the War Between the States, or the War of the Rebellion, or simply the Civil War, was fought from 1861 to 1865. Slavery was over in the US, at least the war was over and the Africans in the US would no longer be used as slaves.

There was slavery in Cuba as well. 

Following the end of the Ten Year War in Cuba there was unrest which resulted in the abolition of slavery in 1886. Long before Castro was even born. The country became a boom town with more and more tenant farmers taking over the plantations of the wealthy. Some wealthy landowners remained, but, during that time the economy was growing because production was increasing due to the Middle Class and the new farmers willing to make their land work for them. The Cuban economy was so vibrant during those years it attracted American investors. They invested in sugar production, tobacco and mining. The oddity is that Cuba was still a Spanish possession. It was for long after Americans became interested.

Four US Presidents tried to purchase Cuba from Spain, but, to no avail. 

...The central leaders (click here) of the 1895 Cuban revolution were Maximo Gomez, ,Calixto Garcia, and Jose Marti. Gomez (1836-1905), who had dedicated more than half of his life to make Cuba free, became the military leader of the Cuban revolution in 1895. Garcia (1839-1898), one of the best known Cuban insurgents, was an essential factor in the U.S. military's success in Cuba. Garcia provided key intelligence to the United States military, including maps and information about the Spanish officers. Marti (1853-1895), a Cuban émigré who organized the Cigarworkers Party, joined Gomez in 1895 and was killed in action. After his death, Marti became a martyr of the revolution and remains a hero to the Cuban people.

Spain responded to the Cuban insurgency by sending 100,000 soldiers to Cuba in 1895. After the United States government was drawn into the conflict in 1898, the end of Spanish rule became a reality. However, the defeat of Spain and the U.S. presence in Cuba raised new questions for the "Pearl" of the Caribbean—questions that have never been fully answered.