Born Again and have had their sins forgiven.
The one's who have a personal relationship with Jesus Christ.
And those very same people exist in every Protestant denomination and in the Catholic Church, etc.
Just too darn simple, isn't it? Institutions created by us humans complicate things. E.G., by the time St. Francis of Assisi died, the Franciscans and spin-off orders were among the largest real estate holders in Italy! Luther prayed the Rosary. Calvin and Zwingli read St. Augustine.
Newsflash! When ISIS , the Muslim Brotherhood, and the Taliban crucify, or behead a Christian, whether he's a follower of the Missouri Synod, the SBC, a Copt, or a Syrian Uniate Catholic really doesn't seem to matter to these Friends of Barack. Perhaps it ought not to matter too much to us.
Furthermore, God is not a respecter of Denominations, or Human Corporate Bodies such as the Baptists, Methodists or even the Catholic.
God deals with the individual.
Your faithful membership in any church, all of your Good Deeds, your faithful attendance at Sunday Service all are meaningless where Heaven is concerned.
Jesus stated very clearly that those only, who Loved God, would be joining him in Heaven, and that there were many, who did many good works even miracles, that would never see Heaven, because they did not Love God, which a man or woman can only do if they have been forgiven of their sins, been Born Again, received that gift of the Holy Spirit whereby their spirit cries “Abba Father”.