An immersive and realistic option would be the ability to have children with an NPC or player. This way, the Seraphim will have a defined sex, male or female, and if the character dies, you can be "reborn" by controlling their descendant, and you can choose which one if you have more than one child.
Since this is a mechanic exclusive to "permadeath mode," we can think a little further to add more realism and difficulty: Enable age groups: child, young adult, adult, and old. In old age, you can choose to die of a heart attack and then control a descendant. And the ages would have debuffs and buffs for each.
However, in old age you do not die of old age, only of a heart attack if you choose or the adversities of the world. But the NPCs in your family do die of old age, only the playable character and other NPCs (traders) in the world do not die of old age.
