I propose, children would be given responsibilities early on, they had to start soon. So, maybe being a father at figure 65 months means teaching a brother or cousin or other newborn and leaving the adults care for the food. They would form trust for one another while the resentment from biological parents towards their children, as shown with gods fury over adam and eve, would be mutual. "Alter" (older) in german can mean big brother, or father, but generally any subjectively old one.

Of course I mainly agree to the story aspect, but I don't know any other mysticism about the mentioned figures.