From the Article:
Abram Petrovich Gannibal
Was an African prince, before he was captured and brought to Russia. After being brought to Russia he became the son, by adoption, of the Russian czar, Peter the Great. As an adult, he held positions such as, major-general, military engineer and governor of Reval, renamed Tallinn, a city in Estonia. His education was completed in Paris. He studied, art, science, and mathematics. He was the great-grandfather of Alexander Pushkin, a great Russian poet and the author of a novel, that he never finished, titled, Peter the Great's Negro.