Pippa Middleton pregnant, expecting third child with husband James Matthews

Pippa Middleton is expanding her brood.

The sister of Kate Middleton, the Duchess of Cambridge,

was spotted at the star-studded “Party at the Palace” concert in London Saturday with a noticeable baby bump.

A source told Page Six that the couple is “so happy” and Pippa is a “natural mama.”

Pippa, 38, married James Matthews, a hedge fund manager and heir to the lairdship of Glen Affric in 2017. They share two children, Arthur, 3, and Grace,

She is reportedly very close with her older sister, Catherine.

The columnist shot to global fame when she served as a bridesmaid when Catherine married Prince William.

Her pert posterior nabbed massive attention when she wore a form-fitting Alexander McQueen gown to the 2011 nuptials.

She even wrote about the ensuing media attention comparing it to Kim Kardashian’s bottom.