system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] Why does Luke not grieve his aunt or uncle, but when Ben dies he gets all super-sad?
gpt
Grief is a peculiar thing. It doesn't happen all of a sudden. True grieving takes a while to set in. Luke was basically in shock when he saw that Beru and Owen had been killed. Then he made an impulsive decision to go travelling with Obi-Wan, and his mind was kept occupied by all the travelling/adventures they were having.  

Basically, he didn't have time to properly grieve until much later, and we're just not shown his grieving process in the film.