Well if you didn't pick it up yet, the older sister and mother were getting it on with the brother before the coma. If he doesn't remember anything probably not a good idea to just dive back into that without figuring out if he's ok with it again, and incest feelings is probably something that is developed but held back over time, it's not a lightbulb moment where you just decide to do it out of the blue.
Kate's depressed, take a wild guess what it's about and why she doesn't want to talk about it at the moment. Mother's financial troubles, take a wild guess what she may be doing now to make money, just going by way she dresses and the shoes in her closet, wonder why she wouldn't want to talk about it yet. Eva and mc were still together at the time of the accident, but she mentioned things have changed, but she obviously still has feelings for him and probably doesn't want to lay the heavy shit on him yet.
There's hints that the mc might be into more heavier shit, like the couple in the mall that reacted oddly to him. A little mystery to start the story is not a bad thing, and it's still very early in the story to be writing it off as bad, just because you didn't get a full backstory on the first screen. Relax, enjoy the ride of the mystery playing out. Game is still better than 80% of the crap you can find on here.