A more thorough explanation:

Definition: Fraternal is an adjective that describes something related to brothers or a fraternity or fraternal benefit association.

Examples:

• My fraternal twin brother and I have a special bond.
• The fraternity held a fraternal gathering to celebrate their brotherhood.
• The fraternal benefit association provided financial support to its members in times of need.

The first example illustrates the first part of the definition, as it describes the relationship between brothers. The second and third examples illustrate the second part of the definition, as they describe a fraternity and a fraternal benefit association, respectively.