User blog comment:Miskos3/Fairy Tail 514: Dragon Seed, Review/@comment-5894890-20161212174423/@comment-7418318-20161212182252

My guess/theory is that Belerison sacrificed himself or was killed in the attempt to save Irene from turning into a Dragon and she took up his name as a sur-name to honor his memory.

Either that or she turned into a Dragon and married him. ^^