Lily Tucker-Pritchett, the adoptive daughter of Cameron and Mitchell, was not "removed" from Modern Family; rather, the original actors who played her departed the show.
The Departure of the Original Lily
For the first two seasons of Modern Family, the role of Lily was shared by twin actors Jaden Hiller and Ella Hiller. They portrayed the character as a baby and toddler, quickly becoming a fan favorite due to their adorable on-screen presence.
Why the Change Happened
The reason for their departure before Season 3 was a decision made by their parents. It was observed that the Hiller twins had stopped enjoying the demanding process of filming a television show. To prioritize their children's well-being and happiness, their parents opted not to have them return for the third season. This led to the role being recast.
The Recasting of Lily
Following the Hiller twins' departure, the character of Lily was taken over by Aubrey Anderson-Emmons. She joined the cast in Season 3 and continued to play Lily throughout the remainder of the series, growing up on screen and becoming a more prominent character with speaking lines and storylines as she aged.
The shift in actors was a notable change for viewers, but it allowed the character of Lily to evolve from a non-speaking infant into a key family member with her own distinct personality and comedic timing.