Genetics calculator
How likely a child is to be born with a parent's congenital trait — Genius, Herculean, Beautiful, Giant… — from the game's own childbirth rules, for one child or several.
In Crusader Kings III a child inherits a congenital trait outright with 80% chance when both parents have it, 50% when one has it and the other carries it, 25% when only one has it; if that fails it may carry it hidden. When both parents have a leveled trait, 40% of their children are born one level up (the 80% who inherit it × 50% reinforcement). Patch 1.20.1.2, from game/common/defines/00_defines.txt (NCharacter, NDomain, NProvince, NChildbirth).
Climbing a trait: two parents at the same level
Genius + Genius
80% a child is Genius too
From two Quick parents to a Genius heir is 2 level-ups. Expected generations, if each generation the heir is the child who went up and marries someone of the same level: 2 children: 3.1 (2.6 with Convergent Blood); 3 children: 2.6 (2.2 with Convergent Blood); 4 children: 2.3 (2.1 with Convergent Blood).
Your parents, your trait
| The child | One child | At least one of 3 |
|---|---|---|
| Genius (one level up) | 40% | 78.4% |
 Intelligent | 40% | 78.4% |
| Carries Intelligent without showing it | 20% | 48.8% |
| None of these (a lower level is possible — not computed) | 0% | 0% |
The inheritance table
| Parents | Born with it | Carries it | Neither |
|---|---|---|---|
| Both parents have it | 80% | 20% | 0% |
| One has it, the other carries it | 50% | 50% | 0% |
| One has it, the other neither | 25% | 56.3% | 18.8% |
| Both carry it | 10% | 45% | 45% |
| One carries it, the other neither | 2% | 24.5% | 73.5% |
Every congenital trait and what it gives · Dynasty legacies (Blood)