Who is the second Kingsguard at the Tower of Joy?

Question

It is fairly well established that Arthur Dayne is the Kingsguard that wielding two swords, however in the books we are told there were three members of the Kingsguard present:

He dreamed an old dream of three knights in white cloaks... They were seven facing three, in the dream as in life... Ser Arthur Dayne, the Sword of the Morning, had a sad smile of his lips, the hilt of the great-sword Dawn poked up over his right shoulder. Ser Oswell Whent was on one knee sharpening his blade with a whetstone, across his white-enameled helm the black bat of his house spread it wings. Between them stood fierce, old Ser Gerold Hightower, the white Bull, Lord Commander of the Kings Guard. - A Game of Thrones, Chapter 39

1. Arthur Dayne
2. Gerold Hightower
3. Oswell Whent

In the show there are only two...

My guess is that the second is Oswell Whent because in the opening scene he is shown "sharpening his blade with a whetstone" and is not "old". Can this be confirmed through scripts or credits?

Bonus question that I know might be answered in the next episode, or is just a cutting of characters as D&D are want to do: Where is Ser Gerold, being Lord Commander, one would think his inclusion would have had more impact...

Answer 1

The second is Ser Gerold Hightower, the actor who played him has confirmed this on Twitter.

@EddieEyre: 'Gerold Hightower' was on my contract if that helps :)

_{Twitter, @EddieEyre}

Ser Oswell Whent was apparently in Dorne and died there but it's unclear when or how this happened but it must have been around the time of the Tower of Joy too. In Season 4 Episode 1, "Two Swords", we see Joffrey leafing through the Book of Brothers. He stops on Ser Arthur Dayne's page but the page on the left looks to be that of Ser Gerold Hightower. It says the following:

Died in the Red Mountains of Dorne alongside his sworn brothers, Ser Arthur Dayne and Ser Oswell Whent.

After refusing to bend the knee to the new king Robert Baratheon, all three were defeated by a small force led by Lord Eddard Stark of Winterfell.

Answer 2

Per IMDb the 2nd Kingsguard is Gerold Hightower. As for the question of where the last Kingsguard is, I'm not sure that this can be answered at the moment. In the books Whent is at the Tower of Joy, in the show he hasn't been mentioned yet.