Here is a brief explanation: More detailed information is contained in several other posts in this blog. God bless!
Think Jacob, Rachel and Leah. Rachel being the kingdom saints under the Kingdom gospel, after the cross, and Leah being the grace saints. Jacob as a picture of Christ.
All of the Bride is in the Body of Christ, but not all the body is the Bride. “children of the Bride chamber” and “friends of the Bridegroom” are OT saints. All one family, all one church. The Bride comes out of the body, just as Eve came from Adam. (Eph 3:5)
The story of Naomi and Ruth helps explain it. Ruth was a Gentile, Naomi’s daughter by adoption, and Naomi (Israel, “the mother of us all”) and Ruth became “joint heirs” when Ruth married Boaz, Naomi even became a wet nurse to her grandchildren.
Adam, John the Baptist, and the OT saints will be at the marriage of the Lamb in Rev 19 as “friends of the Bridegroom”.
The OT saints will reside in “the New Jerusalem”, the Tabernacle of God in Rev 21:3, while the Grace saints will also live in this SAME Tabernacle, but in the Holy of Holies, “the Holy Jerusalem” (found in the KJV only) the most Holy place with Christ as “the Lamb’s wife” Rev 21:7-9. The hypers completely reject what I just said, mainly because it totally contradicts their doctrine, and they have what I call “pigeon holed doctrine” because they completely ignore the OT shadows and picture types previously mentioned, that God uses to teach and illustrate things to us.
They ignore the OT, then turn right around and use it as a reference to say The Nation Israel is the Bride of Christ.
Then there’s those “two programs” they crow about, the “mystery program” and “kingdom program”. there are no “separate programs”, we are all one in Christ Jesus.
The only “mystery” given to Paul being this : That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel: Eph 3:6. understanding the Tabernacle in Rev 21 is the key. (See my Rev 21 blog post). God Bless you!!