Correct me if I'm wrong but Jaehaerys II Targaryen is missing from the got wiki.
I did some research and I found from other wiki pages that Jaehaerys was actually the Mad King's Father and Aegon V his grandfather (who is called the Mad King's father in this wiki)
Considering that some people believe that Lyanna may have said to Ned that Jon's true name is Jaehaerys, we should know that it was given to Jon from Rhaegar's grandfather.