Timeline: L.A.
Please note, this is an AU (Katie!verse) of an AU (House of TM) of an AU (TM!Marvelverse) and nothing listed here should impact the current TM!Marvelverse storyline. It is one possible outcome. Anyone who wants to interact with Katie as their future-self can do so, anyone unrelated who wants to interact with her as if now is now can do so. And you never know, it's Marvel, she could be dropped in to now now ten years older at any moment.
Birth to Age Three
Katie was born to Alex and Lorna Summers is an alternate universe created by Lorna's older sister, the reality-warping Scarlet Witch, Wanda Maximoff. She was born in Hawaii and lived most of her three years on a boat with her scientist parents. Katie was a happy, if lonely, child who loved the water. When her universe collapsed, Katie was rescued by her aunt and placed in a static chaos bubble between the fabric of the universes. Wanda intended to merge Katie with a child born to Alex and Lorna in the prime timeline but when their marriage crumbled she realised she could no longer maintain the bubbleverse and brought Katie to Lorna's friend, Jean-Paul.
While in the bubbleverse Katie visited Lorna in her dreams; when Jean-Paul brought the girl to Lorna they recognised each other immediately. Lorna chose to raise the girl as her own and alone. Alex was told of the girl's existence but chose not to be a part of her life.
Age Three to Six
Months after taking Katie in, Lorna met and fell in love with Henry Hellrung and moved herself and Katie cross country to live with him in the Order's headquarters, The Demeter. Lorna had a number of projects in addition to working part-time with Wayne Enterprises, L.A. and pursuing her PhD and got Katie a nanny, Ana. Closer to the Pacific Ocean that she remembered from early childhood, Katie thrived in L.A. She took classes in pottery and gymnastics and Ana taught her ballet. Surrounded by vocational super heroes and dragged around to all her mother's charity events (usually willingly) Katie grew up with a more global worldview than many of her peers.
Lorna and Henry married when Katie was six years old. She was the flower girl in a quiet beach ceremony on New Year's Day.
Age Six to Thirteen
Henry retired from the Order and the family move out of the Demeter. Lorna remained an active reserve though she took a year off to have a baby, Katie's little brother William Henry Hellrung. Henry successfully ran for US Congress. When Katie was twelve and Will was five, Lorna returned to full active status as a superhero while also working out of Mullholland House. Katie started working afternoons at Mullholland and instituted a pet program. Katie continued with gymnastics and eventually decided to take up surfing.
Age Fourteen
Katie begins high school, still working at Mulholland and surfing competitively. She lives with her mother (Adjunct Scientist w/ WE; Active Superhero; Community Organiser), stepfather (US Representative, state of California) and little brother in Southern California.