And now, following months of speculation, the bride-to-be has finally confirmed that her niece and nephew will be given these roles on her big day on May 20, when she ties the knot with financier James Matthews at St Marks' Church in Englefield, Berkshire.
Spencer Matthews, James's reality TV star brother, will be best man, but it's also been confirmed that there's no official role for Kate, despite Pippa acting as her bridesmaid when she married William in 2011.
According to tradition, Pippa would have to make Kate the maid of honour rather than a bridesmaid, a role that goes to an unmarried female family member. However, the royal was said to be anxious not to upstage her younger sister, 33, on her big day and although at one point she was rumoured to be giving a reading, a source has confirmed that she will be taking a backseat during the nuptials.
Royal fans have been eagerly hoping to see Princess Charlotte as an adorable bridesmaid and proud Prince George accompanying Pippa down the aisle as page boy.
However, the royal was said to be anxious not to upstage her younger sister, 33, on her big day and although at one point she was rumoured to be giving a reading, a source has confirmed that she will be taking a backseat during the nuptials.