The youngest child in a family; the baby of the family (the youngest sibling).
彼女は家族の末っ子で、兄が二人いる。
She is the youngest in her family and has two older brothers.
末っ子は甘やかされがちだと言われる。
It's said that the youngest child tends to be pampered.
末っ子の特権で自由にしている。
He's enjoying freedom as the youngest child's privilege.