The socialite was joined by, Spencer Matthews, and a mystery lady as they enjoyed the warm weather.
Pippa was seen with her new son, Arthur, and other family members as they are currently staying at the family's luxury hotel.
Her husband James Matthews was also spotted cuddling their 11 weeks old baby boy.
But it looks like her 31-year-old brother wanted to take a break from the family as he went for a jog with his friends.
The whole family has arrived in St. Barts as they prepare to see in 2019 together.
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The trio went for a jog on the island close to the family's famous hotel.
Pippa's brother, James, looks to be in great shape as he worked-up a sweat with his run.
His two companions were seen laughing and joking as they kept up with him.
Spencer Matthews, 30, also looked in like he loves to stay fit as he ran beside James and their female companion.
Pippa's sister, Kate Middleton, is staying In Great Britain to be with the Royal family.
Pippa looked radiant after giving birth to her first child with her husband.
Both of her parents, Carole and Michael, were seen with grandson Arthur as they celebrated with their friends and family on the Caribbean island.
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