One of the men pictured with Kate, the shorter, stockier man with the dark curly hair in background photos is William's dear friend Tom von Straubenze. (There are pictures of him walking behind Kate in the winner's circle?? or the grounds, or whatever it's called. The press usually don't identify him, but he was identified when he accompanied William on an official trip to New Zealand last year, I believe.) He attended William's passing out with Kate and her family, Tom was also with William and Kate in Zermatt last week. He is extremely close to William.
The taller dark haired man who is prominently pictured standing with and talking to Kate in the Royal Box is someone I don't know. Well, I don't know any of them, but I do know of von Straubenze as he has been identified as William's very close friend. His brother -- who I think was a friend of William and Harry -- died tragically in a car accident on a road near Highgrove several years ago, I believe. He was 19 or something like that. Tragic.
Anyway, one of William's close pals (often von Straubenze, James Meade, Guy Pelly
, etc.) is usually discretely riding shotgun with Kate at an event when William is not there, or even when William is there. I've read they sort of watch over her for him, which I think is very nice.
And I agree I just love how this young woman handles herself. It is really a testament to her upbrining. Her mother Carole is berated as a gum chewing social climber, which is amazing as she has yet to utter a word, but if she raised a young woman like Kate, she can't be all bad.