What is a cousin?

Collateral blood relatives within three generations

The so-called collateral blood relatives within three generations refer to relatives who trace back to the same blood and count down three generations. For example, if the man himself and his cousin belong to several generations of collateral blood relatives, the individual can first trace back to his grandparents who have the same blood relationship with his cousin through his mother. Grandparents are the first generation, counting backwards to my cousin's mother, that is, my aunt, who is the second generation, and counting backwards to my cousin, who is the third generation. The man himself and his cousin are collateral blood relatives within three generations, and marriage is prohibited according to law. According to this calculation, brothers and sisters, cousins, cousins and uncles within three generations are collateral blood relatives, and marriage is prohibited.

Your uncle or aunt's daughter is older than you, the younger one is your cousin, your uncle or aunt's son, the older one is your cousin, and the younger one is your cousin.