Thank you for the detailed comment!
You actually got everything right for the bonus challenge, so the issue was entirely my mistake. Really sorry for that!
I had the entire family tree scribbled down on my notebook, and used it as a reference while drawing the pedigree chart for the game, but I somehow completely overlooked Mrain. I think that’s what’s causing the bug.
I'll work on a patch update right away. As for coloring the links that have already been clicked, that's a great idea (I can't believe I didn't think of it)! I'll include that in the update as well, along with fixes for the Analyze button and the other smaller issues you mentioned.
*SPOILERS BELOW*
As for the document “Explaining Death,” it’s actually referring to Selinar, who was murdered by an anti-Impure group. His fate is hinted at in a few subtle ways:
In “Wretched Land” Selinar’s father warns him against staying in Merrithel, because the nobles are growing restless from the thought of an Impure being among their higher ranks, and, on top of that, being the father of the last possible heir.
It’s also very subtly hinted at in Mercian’s letter. Mercian says that people told him Vilan was dead, but then she turned out to be a Mutant. He then asks if that means his father is a Mutant too, hinting at the fact that his father is dead (being a child, he doesn’t fully grasp the concept of death, and that was his train of thought).
Now that I think about it, this may be unnecessarily confusing for players, since the document “Explaining Death” is among the first documents that can be opened, and thinking about who died and for what cause so early in the game might distract from the main mystery. I’ll consider making this document appear later in the game from a more relevant document (probably “Wretched Land”).
Congrats on completing the challenge, and good luck on your game dev journey!