Our advice for them is that they marry off to those that are suitable, whether they are from their tribe or not, because of the saying of Allaah the most high:
"O mankind! We have created you from a male and a female, and made you into nations and tribes, that you may know one another. Verily, the most honourable of you with Allah is that (believer) who has At-Taqwa [i.e. one of the Muttaqoon (pious - see V.2:2). Verily, Allah is All-Knowing, All-Aware."
And his the Most High's saying:
"And it is He Who has created man from water, and has appointed for him kindred by blood, and kindred by marriage. And your Lord is Ever All-Powerful to do what He will."
And the saying of the Prophet, salla Allaahu 'alyhi wa sallam: "All of you are from Adam and Adam is from soil" and other proofs from that chapter that show that suitability is in the deen, not in tribe, linage, money, hierarchy, diplomas, studies, profession or occupation.