Which Targaryen has the dragon Rhaegal named after him?
Rhaegal is named for Rhaegar Targaryen, Daenerys Targaryen's eldest brother.
Instruction: Which Targaryen has the dragon Rhaegal named after him?
Context: 
Response: Rhaegal is named for Rhaegar Targaryen, Daenerys Targaryen's eldest brother.