Kate Middleton is officially an aunt. The Duchess of Cambridge's sister, Pippa Middleton, gave birth to her and husband James Matthews' baby boy on Monday, according to her representative.
The baby was born in the Lindo Wing at St Mary's Hospital in London at 1:58 p.m. Monday, weighing 8 pounds and 9 ounces, the news outlet reports.
Both Pippa and the baby are reportedly doing well.
"Everyone is delighted and Mother and baby are doing well," Pippa's representative told PEOPLE.
The baby boy makes Middleton an aunt for the first time. The duchess welcomed her and husband Prince William's third child in April in the Lindo Wing as well. In fact, all three of Middleton and William's children have been born there.
The new baby will have plenty of playmates around; in addition to Middleton and William's kids — Prince George, Princess Charlotte and Prince Louis — Matthews' younger brother, Spencer Matthews, welcomed his own first child with his wife Vogue Williams in September.
Pippa and Matthews married in May 2017 at St. Mark's Church in Englefield. Prince George and Princess Charlotte served in the bridal party, much like they did last week during Princess Eugenie's wedding in Windsor.
A source told PEOPLE in 2016 that Pippa and Matthews were looking forward to settling down and "having children and leading a quiet life."
“I was lucky to pass the 12-week scan without suffering from morning sickness. That meant I was able to carry on as normal,” she wrote.0comments
She documented her fitness regime in her ongoing column for the magazine, writing at the beginning of her third trimester that swimming had become part of her routine.
“From personal experience, I’d confidently say I find it has been the most enjoyable and rewarding form of exercise since I found out I was expecting,” she wrote. “It’s comforting to know that it’s safe throughout pregnancy, and you don’t need to adapt and change too much (unlike most other sports). It’s so good for you that you could swim every day – as long as you don’t overexert yourself – right up until the end of the third trimester.”