Jesus clarified the basis for judgment then. It would be reception or rejection of the King as seen in people"s reception or rejection of the King"s brothers. The King"s brothers are probably His faithful disciples who fulfill His will by preaching the gospel of the kingdom during the Tribulation (cf. Matthew 12:48-49; Matthew 28:10; Isaiah 58:7). Most of these will be Jews, including the144 ,000 , though some may be Gentile converts as well (cf. Revelation 7:1-8; Revelation 14:1-5). They will have become believers following the Rapture since all believers alive on the earth when the Rapture happens will go to be with Jesus then. [1] Other interpreters have identified these brethren as all the needy of the world, [2] all Jews, [3] or Christian apostles and missionaries. [4][source]
"Those described here are people who have lived through the great tribulation, a time of unparalleled anti-Semitism, when the majority of Jews in the land will be killed. Under these circumstances, if a Gentile befriends a Jew to the extent of feeding and clothing and visiting him, it could only mean that he is a believer in Jesus Christ and recognizes the Jews as the chosen people." [5][source]
The least of Jesus" brothers are probably Jewish Tribulation martyrs. [6][source]