Juste is Richter's Grandfather.
Pretty much. People back in those days were getting married in their late teens and having children not long after the fact. There was no guarantee that anyone would be living a long and healthy life. The era when Juste lived was still very questionable in terms of good health, proper diet, access to medicine, keeping clean regularly, etc. It makes far more sense that Richter is Juste's grandson as it would be just too short a time period between HoD and RoB otherwise.