Jesus had promised that the each of the disciples would rule over one of the tribes of Israel.
Matthew 19:28
And Jesus said unto them, Verily I say unto you, That ye which have followed me, in the regeneration when the Son of man shall sit in the throne of his glory, ye also shall sit upon
twelve thrones, judging the
twelve tribes of Israel.
From there it may have been assumed that there was a tribal connection. However, another prophesy tells that Israel would always have a ruler descended from the House of David.
Jeremiah 33:17
For thus saith the LORD; David
shall never want a man to sit upon the throne of the house of
Israel; (this is a millenial prophesy).
As most of the disciples were descended from the tribes of the southern
kingdom of Judah it may well be that they are all considered "of the house of David" for the purpose of later rulership.
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