Thanks for your question.
The "other sheep" are the Gentiles. Jesus in his earthly ministry was sent to the lost sheep of the house of Israel. (Matt. 15:24). It was prophesied, however, "He shall bring forth judgment to the Gentiles" (Isa. 42:1), and that he would be given as "light to the Gentiles". (Isa. 42:6 R.S.V. cf. Matt. 12:18-21). The Gentiles heard the voice of the Shepherd through the labours of the Apostle Paul, a man especially chosen for this work. (Acts 9:15; 1 Tim. 2:7 cf. Acts 18:6). The only two communities of believers ["folds" if you like] mentioned in the New Testament are the Jews and the Gentiles. As Paul puts it in Romans 1:16 "I am not ashamed of the gospel, because it is the power of God for the salvation of everyone who believes: first for the Jew, then for the Gentile." [NIV].
I hope that answers your question.
God bless,
Mike