Pippa Middleton is reportedly expecting her third child.The socialite, who is the younger sister of Catherine, Duchess of Cambridge, attended the Party at the Palace event alongside her husband James Matthews and other members of their family in celebration of Queen Elizabeth II’s Platinum Jubilee on Saturday night. Pippa was photographed wearing a green dress which showcased her growing baby bump. Representatives for the 38-year-old declined to comment on the news, but multiple sources confirmed the pregnancy to editors at People. Pippa and James tied the knot in 2017. They are already parents to Arthur, three, and Grace, 14 months.