This is a sugestion for when the basic principal mission its done, but in the game, we can have a bunch of pregnant women, with their own races, skills and others things, and, in some point, we will need a successor, so i think that will be a nice idea to make other options to how we choose who will be, but the one that i think its the most interesting option if we can make a competition, basically sending a letter to every son we have (or to every woman we fucked, because ryen probably won't meet every son that he have or even don't know to every woman that he makes pregnant) inviting them to this competition, testing their intelligence, strength, magical capacity, and others to see who is worth to be given the crown of king saotome, i think that our choices along the game need tho affect directly our sons, for example, if we choose that the elf from our group (mira i think) will be a druid, their son will be more magical, and if we choose that she will be a archer, their son will be a more phisical fighter, because she will teach him what she know, i have in mind that draconians live VERY much, and ryen its a pure draconian (i think), so i know that is a little hard to think of him older than their son, but he could make this thing for other reason than old age, for example, he could make this because he can be a king, but he is a adventure too, and he know that someday he can be killed, so he already take a worth successor in any case.
Note:i think you should put this in some type of paid DLC, because you will problably need to work your ass off to make this. Also, im sorry for my bad english im brasilian.
