Paul Anthony Kelly , who recently rose to prominence playing John F. Kennedy Jr. in FX’s “Love Story,” is joining another Ryan Murphy series at the network: He has been cast in Season 13 of “ American Horror Story .” Kelly announced the news himself at Disney’s annual presentation to advertisers at upfronts in New York City, during which “American Horror Story” stars Sarah Paulson, Evan Peters, Angela Bassett, Gabourey Sidibe, Billie Lourd and Emma Roberts were flanked by hooded Druids before Kelly emerged and said, “I guess every nightmare needs fresh blood, and 13’s my lucky number.” Full plot details for “American Horror Story” Season 13 have yet to be announced, with FX’s current logline reading: “Which iconic horrors will return to haunt the hallowed halls of 13 and what new terrors await? Light your candles, draw your pentagrams and prepare for a supreme surprise.” Popular on Variety However, it is known that the season will feature the return of several fan-favorite characters.…