Rhaegar Targaryen was killed by Robert Baratheon in single combat during the Battle of the Trident at the ruby ford, so named for the jewels from Rhaegar’s armor that filled the river after he was struck by Robert’s warhammer.
Rhaegar was the son and heir of King Aerys II, better known as The Mad King, and the older brother of Viserys and Daenerys (Emilia Clarke), who was born after Rhaegar's death. He was popular, intelligent, bookish and a noted musician.
Tywin Lannister had planned to marry Cersei to Rhaegar. However, Aerys shot down the idea as being beneath his son. Instead, Rhaegar was married to Elia Martell, Oberyn and Prince Doran's sister. Elia loved her husband and she had two children with Rhaegar, a daughter, Rhaenys, and son, Aegon.
Rhaegar Targaryen could end up playing a huge role in Game of Thrones, even though he’s no longer alive. He ties directly into a theory involving Jon Snow and the Tower of Joy. Learn more about Rhaegar along with spoilers through the season 6 finale and spoilers if any of these theories are true at Heavy.com.