The Princess Royal is the mother of Peter Phillips, 44, and Zara Tindall, 40, while the Duchess has Prince George, Princess Charlotte and Prince Louis.
The Duchess, patron of the Royal College of Obstetrics and Gynaecology, has made child development a cornerstone of her work in the Royal Family, finding common ground with her aunt-in-law.
Both women are among the most popular members of the royal family. The work of the Duchess is widely covered by the media, while the Princess is considered the most hardworking by consistently fulfilling her commitments.
Jo Tanner, spokesperson for the Royal College of Midwives, said of the Princess: “She really understands motherhood and midwifery, so she can speak with authority about it. Our members absolutely love her because she cares so much about it.