My opinion/theory, even if people think it's controversial, is that the MC's Mom was a Burgmeister and the sister of Rusty's Dad which will make the MC and Rusty cousins, and the grandparents are reaching out to him to apologise for everything that happened with his Mom and offer him an inheritance that will make him wealthier than Rusty. We'll then either decide if the MC accepts it or not, or he'll simply be given it and it will influence how characters like Rusty, Jill, Quinn, etc, perceive him, and at the end of the game we'll decide whether to keep or give it up.