Pippa Middleton is single; watch out Prince Harry!

Pippa Middleton, the royal sister-in-law who has us every bit as enthralled as her sister, Kate Middleton (aka Catherine, Duchess of Cambridge), is apparently a free agent again after splitting with her on-again/off-again boyfriend Alex Loudon... again.

And, to add a bit of intrigue, the split was allegedly prompted by Pippa's new status as a sex symbol and her unashamed flirting with her new in-law, Prince Harry. The couple supposedly had a "blazing row" at a friend's wedding over the summer, reports the U.K.'s Sun, and has been squabbling ever since.

"Pippa tried to get over the split by spending last weekend with Wills and Kate at Balmoral," a source tells the Sun. "She and Alex split briefly in the summer -- but this time it's over. They are barely speaking."

Prince Harry, it should be noted, is currently in the U.S. completing a helicopter training course and doing his best to avoid fornicating with girls in small Arizona towns.