>>149918377
What we know is that:
>Lily and Jack are 11 and 13 years old and roughly 2 years apart. That could mean anything from Jack is 1 year and 1 day older to Jack is 2 years and 364 days older.
>Jack had semi-regular contact with Lily, Will, and Minju since he was a small child, but hasn't seen his father in 7 years since he was 6 years old.
>Jack has his father's surname even though his mother seems to mostly have the custody.
>Jack was constantly globetrotting with his mother.
>Will and Minju can be quite the couch potatoes.
>Will said in "Father, Son and Furniture Store": "Jack says he wants a hammock to go with his life of adventure. I don't know anything about adventure. That was his mom's thing. What's my thing?" This indicates that Alice was always into adventures while Will was more grounded.
>Alice trusts her ex Will enough to send her son to his father during the summer.
>There don't seem to be much if any resentment between Alice, Will, Minju, and Jack. And on Lily's part, her dislike of the situation was more about Jack moving into her "gamer room".

My theory/personal headcanon is that:
>Around 2 years before Jack's birth, Alice and Will started dating.
>9 months before Jack's birth, Alice got pregnant.
>Some time after Jack's birth, Will wanted to marry and settle down with Alice but Alice wanted to continue/start her globetrotting, so they broke up.
>Rather fast after the break-up, Will met Minju.
>Around 1 to 6 months after their first date Minju got pregnant.
>They married and moved into their house.
>Around 1.5 years to 2.5 years after Jack's birth, Minju gave birth to Lily.
>Alice, still having friendly contact with Will, sometimes dropped off Jack by Will, Minju, and Lily.
>Jack after age 6, seeing his mother as a role model, wants to stay with her and travel around the globe rather than being with his father, leading to him and his father not having met for 7 years.