The ROCOR and the OCA are BOTH spiritual children of the Moscow Patriarchate. The Bolshevik Revolution and resulting Communist persecution of the Orthodox Church in Russia after 1917 fragmented Russian Orthodoxy and that still affects us to this day. What is today the OCA was in 1917 the North American Diocese of the Russian Orthodox Church. After the Communist Revolution in Russia, Patriarch Tikhon (who had been Bishop of the North American diocese and had a very close connection with the Orthodox in America) told the North American Diocese to "believe NOTHING from Moscow until the Church in Russia is free." Then the Communists murdered Patriarch Tikhon and installed a puppet bishop in his place who demanded that the Orthodox in America take an oath of allegience to the atheistic Soviet gov't! The North American diocese snorted at such a notion, and at the Cleveland Sobor declared itself as "temporarily self-governing" until the matter could be settled.
Our dear ROCOR brethren have a different origin. They were mostly Russians from Russia who fled to the West when the Communists began killing off all the Orthodox bishops and priests. They included Metropolitan Anthony Krapovitsky, the Bishop of Kiev. After fleeing to Constantinople, the ROCOR people eventually found refuge in Serbia, where they re-constituted themselves with a Holy Synod of Bishops at Karlovsky. From there, ROCOR moved to Germany for a while, and then finally to Jordanville, New York, where Holy Trinity Monastery and Seminary is located.