The two major examples being the marriage between King Emeric of Hungary and Constance, daughter of King Alfonso II of Aragon, in 1198, and then the marriage between King James I of Aragon and Violante, daughter of King Andrew II of Hungary, in 1235.
Basically, I wonder why the houses of Arpad and Barcelona would choose to ally with each other when there seemed to be no tangible benefits, their respective domains being on opposite sides of the Mediterranean. Was it a matter of prestige?