Answer:
endogamy
Explanation:
Endogamy: In sociology, the term endogamy is also referred to as in-marriage and is defined as a type of segregation that assists a particular community or group to resist the merging or integrating the process with the member of the other culture or group who does not possess same resource or beliefs.
In other words, it is defined as a ritual of an individual marrying within his or her own cultural, tribal, social, religious, or ethnic group.
In the question above, the given practice is known as endogamy.