Changes the way stat increasing works:
1 parent: 3/4 decrement, 1/4 nothing
2 parents: 2/4 decrement, 1/4 nothing, 1/4 increment
3 parents, 1/4 decrement, 1/2 nothing, 1/4 increment
4 parents: 1/4 decrement, 1/4 nothing, 1/2 increment