Even in the beginnings of this one and only Church of God there arose certain rifts, which the Apostle strongly condemned. But in subsequent centuries much more serious dissensions made their appearance and quite large communities came to be separated from full communion with the Catholic Church — for which, often enough, men of both sides were to blame. The children who are born into these Communities and who grow up believing in Christ cannot be accused of the sin involved in the separation, and the Catholic Church embraces them as brothers, with respect and affection. For men who believe in Christ and have been truly baptized are in communion with the Catholic Church even though this communion is imperfect. The differences that exist in varying degrees between them and the Catholic Church — whether in doctrine and sometimes in discipline, or concerning the structure of the Church — do indeed create many obstacles, sometimes serious ones, to full ecclesiastical communion. The ecumenical movement is striving to overcome these obstacles. But even in spite of them it remains true that all who have been justified by faith in Baptism are members of Christ’s body, and have a right to be called Christian, and so are correctly accepted as brothers by the children of the Catholic Church.

Unitatis redintegratio, added to the Catechism of the Catholic Church here. Emphases mine, of course.