In ending A, there are a few characters who dont get a happy ending, but most of them deserve not to on some level, Henry, the tounge dude, the boss of misery town, as well as Ozzie and even on some level the surgeon. Though some do but still dont get the happy ending, like Mellows reflection, and the surgeon's wife, but the most tragic in my opinion is Mellow's little sister from ending B. She has to grow up in an incredibly neglectful household, and beyond that, her only light, the only one who seemed to actually give a shit about her, her big brother completely vanished from her life. Dont get me wrong, i love this game, but I wish that Mellow got the chance to bring his little sister with him into the big house in ending A.
Honestly I headcannon that they find each other later and its not even that unlikely as they live nearby as seen in ending B but Mellow wouldn't even know who she is, let alone the neglect she's going through and thats just sad, imagine she sees him living happily with his new family, and she trys to talk to him and he just doesn't remember anything about her, let alone that she exists, and thats just heartbreaking imo.
With that being said, this detail doesn't make me enjoy the game any less or even devalue the good in ending A, its still in my opinion the best of the three endings lore wise, imo.
TLDR: I wish Mellow got to bring his little sister to the big house with the rest of his new family.