Do I have to pay rent for staying at my cousin's house during the summer vacation?

You don't need to pay rent when you live in your cousin's house during the summer vacation. You can send a small gift to show your gratitude.

Cousin means: among the daughters of father and brother, the older one is called "cousin"

Cousin is the daughter of menstruation. My uncle's is my cousin! Menstrual family is a cousin, and uncle's family is a cousin.

Cousins are my aunt's daughters. Cousins are the daughters of uncles and aunts. Grandparents are cousins. Grandmother and nurse are cousins. Cousins are also called slave sisters. Cousins are also called slave brothers. Menstruation's cousin, menstrual cousin. My aunt's cousin's father. Grandma's cousin. They are all cousins.