Ideas
Same.
Adding: Imaginary Friend relationships are also lost when moving a child to another household. This is despite following the instructions in the AA Lessons: "If a child Sim who owns an Imaginary Friend changes households, they must keep their ImagineMe! Doll in their inventory before moving to preserve their original Imaginary Friend!"
Moved my child into their Grandparents household with the Imaginary Friend in their personal inventory. They lost their relationship. This is despite having already completed the Formative Moment of having a Creative Best Imaginary Friend.
"Had a Creative Best Imaginary Friend (From Formative Moments) As a Child, this Sim imagined up an Imaginary friend out of their ImagineMe! Doll! They formed a special relationship and spent a lot of time doing arts and crafts. As an Adult, this Sim will build creative Skills more quickly."
New Best Friend Krafty Kid. Previous Invisible Best Friend is nameless.
Forgot to say: This is in my regular save and in my vanilla test save.
Also, I know it's not BBF, just too tired of all this to change it.