Gentiles are considered part of Israel:
Rom_11:26 And in this way all Israel will be saved, as it is written, "The Deliverer will come from Zion, he will banish ungodliness from Jacob";
As for which tribe we belong to, like everything else the 12 tribes of Israel were corrupt. God will reconstitute the 12 tribes. I don't mean to post such a long passage but it does explain it here:
Heb 7:2 and to him Abraham apportioned a tenth part of everything. He is first, by translation of his name, king of righteousness, and then he is also king of Salem, that is, king of peace.
Heb 7:3 He is without father or mother or genealogy, having neither beginning of days nor end of life, but resembling the Son of God he continues a priest forever.
Heb 7:4 See how great this man was to whom Abraham the patriarch gave a tenth of the spoils!
Heb 7:5 And those descendants of Levi who receive the priestly office have a commandment in the law to take tithes from the people, that is, from their brothers, though these also are descended from Abraham.
Heb 7:6 But this man who does not have his descent from them received tithes from Abraham and blessed him who had the promises.
Heb 7:7 It is beyond dispute that the inferior is blessed by the superior.
Heb 7:8 In the one case tithes are received by mortal men, but in the other case, by one of whom it is testified that he lives.
Heb 7:9 One might even say that Levi himself, who receives tithes, paid tithes through Abraham,
Heb 7:10 for he was still in the loins of his ancestor when Melchizedek met him.
Heb 7:11 Now if perfection had been attainable through the Levitical priesthood (for under it the people received the law), what further need would there have been for another priest to arise after the order of Melchizedek, rather than one named after the order of Aaron?
Heb 7:12 For when there is a change in the priesthood, there is necessarily a change in the law as well.
Heb 7:13 For the one of whom these things are spoken belonged to another tribe, from which no one has ever served at the altar.
Heb 7:14 For it is evident that our Lord was descended from Judah, and in connection with that tribe Moses said nothing about priests.
Heb 7:15 This becomes even more evident when another priest arises in the likeness of Melchizedek,
Heb 7:16 who has become a priest, not on the basis of a legal requirement concerning bodily descent, but by the power of an indestructible life.
Heb 7:17 For it is witnessed of him, "You are a priest forever, after the order of Melchizedek."
Heb 7:18 For on the one hand, a former commandment is set aside because of its weakness and uselessness
Heb 7:19 (for the law made nothing perfect); but on the other hand, a better hope is introduced, through which we draw near to God.
Heb 7:20 And it was not without an oath. For those who formerly became priests were made such without an oath, Heb 7:21 but this one was made a priest with an oath by the one who said to him: "The Lord has sworn and will not change his mind, 'You are a priest forever.'"
Heb 7:22 This makes Jesus the guarantor of a better covenant.
Heb 7:23 The former priests were many in number, because they were prevented by death from continuing in office,
Heb 7:24 but he holds his priesthood permanently, because he continues forever.
Heb 7:25 Consequently, he is able to save to the uttermost those who draw near to God through him, since he always lives to make intercession for them.
Heb 7:26 For it was indeed fitting that we should have such a high priest, holy, innocent, unstained, separated from sinners, and exalted above the heavens.
Heb 7:27 He has no need, like those high priests, to offer sacrifices daily, first for his own sins and then for those of the people, since he did this once for all when he offered up himself.
Paul also states in Eph 2:11-22 that once we confess Yeshua as Messiah, we are no longer gentiles, but fellow citizens of Israel and partakeers of ALL the covenantS of promise that were made from the beginning. We are equal heirs amd sons and daughters of the house of God.
The term ‘gentile(s)/nation(s)s’ simply means one is who not of God’s covenant, old or new, so this also puzzles me as to why the ‘church’ still considers itself Israel,other than the fact that the early church fathers were anti0semetic and hated everything Jewish because it did not fit their plan of growth for the church.
So if we are sons and daughters and are to be working on being transformed to look like the Son according to the path given through Moses, why are we taught from the ‘church’ doctrines and traditions to reject everything that defines what a son or daughter is to look like and act like?
Another point on the grafting in.
In the account of the Exodus & Wilderness journey we see a man named Caleb chosen as the one to lead the tribe of Judah. Caleb was not of Israeli blood, his father was a Canaanite. It was Caleb’s confessing Yahweh as God as Savior and following His Ways completely that deamed Caleb worthy to be called a ‘son’ and he was only one of two (Joshua being the other) of the original millions that left Egypt who actually entered into the promised land. These two represent ‘the remnant’ of the end days.
Narrow is the gate and few find it, Many are called but few are chosen. Why? Because it is easier to look like the ‘nations’ than to be ‘set-apart’ as to stand out from all others, including ones family which Messiah twice told us would happen so we must count the cost first. Are we willing to stand in the same position as Himself and all the disciples who were killed for standing steadfast in the covenant spoken at Mt Sinai by Yeshua Messiah to Moses. (Acts 7:37-39, Heb 3:7-4:13)