"Marc has an older brother who is named Jean-Paul."

Translation: Marc a un frère aîné qui s'appelle Jean-Paul.

[KAZEnoUSAMARU]

The BAGS rule doesn't apply here like "un aine frere"?

[Jojo553168]

No. (It's not really a rule, actually.)

[Sucy-en-Brie94]

Marc a un grand frère qui s'appelle Jean-Paul. Accepted :)