Kate Middleton serves as unofficial bridesmaid at Pippa Middleton's wedding -- see her return the favor!

Six years after Pippa Middleton became the most famous bridesmaid in the world in her all-white gown at her sister, Kate Middleton's wedding to Prince William at Westminster Abbey, the royal returned the favor and was by Pippa's side at her big day on Saturday.

Kate was spotted outside the church with Pippa as she prepped marry James Matthews at St. Mark's Church in Englefield, England.

Rumors initially swirled about whether Kate, 35, would serve as a bridesmaid at Pippa's wedding given her royal stature and celebrity status. But, Pippa, who looked absolutely stunning in a lace Giles Deacon gown, with a long train and flowing veil, eschewed traditions and chatter and had Kate beside her as she prepped to walk down the aisle.

Basically, while Kate was not an "official" bridesmaid, she was the only attendant to Pippa, and was seen adjusting her train to ensure the 32-year-old bride looked absolutely perfect. Kate was also spotted keeping all the page boys and flower girls in line and keeping them quiet before the ceremony.

After the bride and groom said "I do" in the church, Kate, who was clad in a silk, blush pink dress and a matching hat, was also spotted helping Pippa as she exited the church. The traditional photo with her sister by her side looked extremely similar to Kate's own post-ceremony shots.

PHOTOS: All the details from Pippa Middleton's big day

Like the stunning family affair that even the royal wedding was, it looked like Pippa did the same and really leaned on her big sister throughout the day.

And what a glamorous and gorgeous day it was!

PHOTOS: Take a look back at Pippa at Kate's wedding