Cousin:表哥、表弟、表姐、表妹,堂哥、堂弟、堂姐、堂妹。
表哥:a male whose father is your mother's brother is older than you.
表弟:a male whose father is your mother's brother is younger than you.
表姐:a female, whose father is your mother's brother, or whose mother is your father's sister, is older than you.
表妹:a female, whose father is your mother's brother, or whose mother is your father's sister, is younger than you.
堂哥:a male whose father is your father's brother is older than you.
堂弟:a male whose father is your father's brother is younger than you.
堂姐:a female whose father is your father's brother is older than you.
堂妹:a female whose father is your father's brother is younger than you.
If you get confused, it's okay because even Chinese may not figure it out clearly. : P