No. 130 Are non-Catholic Christians our sisters and brothers also?
All baptized persons belong to the Church of Jesus Christ. That is why also those Christians who find themselves separated from the full communion of the Catholic Church are rightly called Christians and are therefore our sisters and brothers. [817-819]
Instances of separation from the one Church of Christ came about through falsifications of Christ's teaching, human failings, and a lack of willingness to be reconciled - usually on the part of representatives on both sides. Christians today are in no way guilty for the historical divisions of the Church. The Holy Spirit also works for the salvation of mankind in the Churches and Ecclesial Communities that are separated in the Catholic Church. All of the gifts present there, for example, Sacred Scripture, Sacraments, faith, hope, love, and other charisms, come originally from Christ. Where the Spirit of Christ lives, there is an inner dynamic leading toward "reunion", because what belongs together wants to grow together.
*Churches and Ecclesial Communities - Many Christian communities on earth call themselves churches. According to Catholic understanding, only those in which the sacraments of Jesus Christ have been preserved in their entirety have remained "Church". This is true especially of the Orthodox and Eastern Churches. In the "ecclesial communities" that resulted from the Protestant Reformation, all the sacraments have not been preserved.
No. 131 What must we do for the unity of Christians?
In word and deed we must obey Christ, who expressly wills "that they may all be one" (John 17:21) [820-821]
Christian unity is the business of all Christians, regardless of how young or old they are. Unity was one of Jesus' most important concerns. He prayed to the Father, "that they may all be one... so that the world may believe that you have sent me" (John 17:21). Division are like wounds on the Body of Christ; they hurt and fester. Divisions lead to enmities and weaken the faith and credibility of Christians. Overcoming the scandal of separation requires the conversion of all concerned but also knowledge of one's own faith convictions, dialogues with others, and especially prayer in common, and collaboration among Christians in serving mankind. Those in authority in the Church must not let theological dialogue be interrupted.