Did the writers forget about Jake’s twin brother?

It’s so bizarre. The inciting incident for the entire saga is that Jake, a “washout” disabled veteran with nothing going on besides being a barfly, learns that his twin brother, a brilliant scientist, has died, and only due to the coincidence of their shared genetics is Jake ordered to take his twin’s place in the Avatar program. Jake is stepping into his dead brother’s shoes, in more ways than one, as he literally inhabits the body that was grown for his twin. This all feels so thematically relevant— not only with plot threads like Lo’ak forever being in his (dead brother’s) shadow, or Quaritch struggling with the idea that he is merely a copy of a dead man, but also in the overall themes of how our fates and destinies are inextricable from our ancestors’ journeys.

And yet the writers NEVER do anything with this. Yes, Jake is resentful of his humanity, but he never mentions or talks about his human family or his dead twin even at times when it would be so narratively germane. There’s no cathartic reveal to Lo’ak that Jake has once suffered a similar loss of a “golden child” sibling. There’s no grief from Jake in knowing that while Neytiri can connect to her dead loved ones through Eywa, Jake will never see his twin again. There’s almost zero mention of Jake’s brother even among the human scientists, who would have ostensibly have been collaborators with him. He was important enough for them to grow a whole Avatar-body for!

Am I missing something? it’s such an obvious thing to explore, it’s RIGHT THERE, and the writers ignore it completely.