Kate Middleton's Parents Join Prince William at Royal Estate

NEW YORK (CBS) Kate Middleton and her parents joined Prince William for a shooting weekend at the royal estate of Balmoral, leaving royal watchers wondering if an engagement announcement could be close.

Photos emerged on Tuesday of Michael and Carole Middleton at the Queen's Scottish estate.

PICTURES: Prince William
PICTURES: Kate Middleton

One of the photos, published by Britain's Daily Mail, shows Carole lying on the ground, learning how to aim a rifle, while Michael looks on.

The Mail suggests that the weekend getaway may be highly symbolic, meaning the Middletons are now welcome in the royal fold.

"That they should be guests at a shooting party should not be underestimated," one figure told the newspaper. "This is the Middletons being taught to be able to join the royals at play."

The invitation would have been approved by William's father, Prince Charles, and known about by the Queen, according to the report.

Other sources concluded that the presence of Middleton's parents was a sure sign an engagement is imminent.

"William and Kate do go up to Balmoral quite a bit, but inviting her parents is a big deal. This is virtually confirmation they're his in-laws-to-be," an insider told the Mail.

Speculation that the two may soon be engaged intensified when the couple stepped out publicly at a friend's wedding last month.