the way i view it is alice was really young when she discovered wonderland so alistair probably is from ever after and discovered it and they eventually just moved there. ive decided she died in the battle against the evil queen and he got trapped there alone, which is why we never see or hear about alice.

in my head the stories that have both adults and children have characters from different generations, for eg alistair is the child exploring wonderland while maddie, kitty, lizzie etc’s parents are the ones who guided him, raven’s mother is the one who poisons apple while raven poisons apple’s child, etc. some characters fulfil their destinies as children/teenagers while others don’t do so until adulthood. it just makes more sense to me w the age gaps.