The twelve tribes are from Children of Israel. Just as the Arabs are called tribes and foreigners are called nations. They are the descendants of The Prophet Yaqoub pbuh who had twelve sons.
(And We divided them into twelve tribes (as distinct) nations. We directed Musa (Moses) by inspiration, when his people asked him for water, (saying): “Strike the stone with your stick”, and there gushed forth out of it twelve springs: each group knew its own place for water. We shaded them with the clouds and sent down upon them Al-Manna and the quails (saying): “Eat of the good things with which We have provided you.” They harmed Us not but they used to harm themselves.) [Al-Baqarah 2: 160]
هم من بطون بني إسرائيل يقال لهم الأسباط كما يقال للعرب قبائل وللعجم شعوب.
(وَقَطَّعْنَاهُمُ اثْنَتَيْ عَشْرَةَ أَسْبَاطًا أُمَمًا وَأَوْحَيْنَا إِلَىٰ مُوسَىٰ إِذِ اسْتَسْقَاهُ قَوْمُهُ أَنِ اضْرِب بِّعَصَاكَ الْحَجَرَ فَانبَجَسَتْ مِنْهُ اثْنَتَا عَشْرَةَ عَيْنًا قَدْ عَلِمَ كُلُّ أُنَاسٍ مَّشْرَبَهُمْ وَظَلَّلْنَا عَلَيْهِمُ الْغَمَامَ وَأَنزَلْنَا عَلَيْهِمُ الْمَنَّ وَالسَّلْوَىٰ كُلُوا مِن طَيِّبَاتِ مَا رَزَقْنَاكُمْ وَمَا ظَلَمُونَا وَلَـٰكِن كَانُوا أَنفُسَهُمْ يَظْلِمُونَ
البقرة 2: 160