The Eucharist

So I was reading on the Watchtower's site about the Eucharist (I was actually trying to find out what they say about Thanksgiving, the U.S. holiday) and I got to the beginning of their explanation on who should partake in communion. How do they go from this:

Primarily, though, the Lord’s Evening Meal is a communion meal. Those involved are (1) Jehovah God, who arranged for the ransom, (2) Jesus Christ, “the Lamb of God,” who provided the ransom, and (3) Jesus’ spiritual brothers. By partaking of the bread and wine, the latter show that they are fully united with Christ. (John 1:29; 1 Corinthians 10:16, 17)

To this:

They also show that they are in “the new covenant” as spirit-anointed disciples of Jesus. These are the ones who will reign with Christ in heaven as kings and priests.—Luke 22:20; John 14:2, 3; Revelation 5:9, 10.

?????????????

Notice also how they provide no quick explanation of #3 of those involved (Jesus' spiritual brothers):

(1) Jehovah God ----> who arranged for the ransom

(2) Jesus Christ, “the Lamb of God,” ---->who provided the ransom, and

(3) Jesus’ spiritual brothers. ----> no explanation of how they came up with "Jesus' spiritual brothers

For the average jw no explanation is needed, they know that "Jesus' spiritual brothers" is jwspeak for the 144,000/FDS.