"삼촌의 자식은 사촌이에요."
Translation:An uncle's child is a cousin.
Thanks Elise. So basically,
아저씨 = term of reference to a man, of probably the same age or older than one's parents and most likely, married
삼촌 = familiar term of reference to an unmarried man of probably the same age or younger than one's parents
형 / 오빠 = familiar term of reference to a male acquaintance slightly older than oneself.