Final Boss is a reflection of yourself that the only way to beat is by trading deathblows, the programmer who teams up with the brother is really the guy behind all of it. He finds out while his sister is fighting the final boss and decides to sacrifice herself to save everyone. The boss dies, she doesn't die all the way and wakes up before and stops the brother from murdering the bad guy over her hospital bed. Gotta do a lot of character work to get there though. They both deal with their demons over the course of the story Boom, I came up with all that just now.
NO. They do not have a child now. NO.