Cousin primes are pairs of prime numbers that have a difference of four. For example, the pairs 3, 7 and 7, 11 are cousin primes because both numbers in each pair are prime and their difference is four. These pairs are a specific type of prime number relationship, similar to twin primes, which have a difference of two. Cousin primes are part of the broader study of prime numbers in number theory, a branch of mathematics that explores the properties and relationships of integers.