From A Wiki of Ice and Fire
|Alias|| "Harry the Heir"|
The Young Falcon
|Allegiance|| House Hardyng|
|Book(s)|| A Feast for Crows (Mentioned)|
A Dance with Dragons (Mentioned)
Harry is said to be very handsome. He has sandy brown hair, deep blue eyes and dimples when he smiles. Petyr Baelish says that a wife of Harry would be the envy of every highborn maiden in the Vale, and a few from the Riverlands and the Reach, as well. 
Harrold was born the eldest son of a landed knight of House Hardyng and the youngest daughter of Alys and Ser Elys Waynwood. He was taken in as Lady Anya Waynwood's ward at Ironoaks and was raised there. Harrold is still young but it's rumored that, despite his youth, he's already fathered a bastard daughter.
Jon's sister Alys had eight daughters and a son. Through an unfortunate series of unrelated events, the boy and four of the girls died young or childless, a fifth had one child who died young, a sixth became a septa, and another became a silent sister. The last, and youngest daughter died shortly after giving birth to Harrold, leaving Robert and Harrold as the last inheritable descendents of Jasper Arryn, and Harrold as Robert's heir presumptive. Should the sickly Lord Robert die without an heir, Harrold would become a member of the house and Lord of the Eyrie and Defender of the Vale.
A Feast for Crows
Gossip holds that, despite his youth, Hardyng has already fathered at least one baseborn child with another on the way. He has been knighted by Lord Yohn Royce after winning a small melee for squires held at Runestone. Petyr Baelish, Lord Protector of the Vale of Arryn, arranged a betrothal between Harrold and Sansa Stark, who was masquerading as Baelish's bastard daughter, "Alayne Stone". He schemes to reveal Sansa's true identity and reclaim Winterfell in her name.
|3rd: Lysa Tully||Jon||2nd: Rowena Arryn||1st: Jeyne Royce||Alys||Elys Waynwood||Ronnel||Lady Belmore|
|Robert||daughter||Denys Arryn||daughter||Ser Hardyng||6 other daughters||Jasper Waynwood||Elbert|
|1 Child||Harrold Hardyng|