Personality inheritance chance of an given source is ~10%, whereas ancestry is guaranteed to be one of the original two sources.

Affinities have a base chance of ~42% of being inherited from either source, and ~16% chance of mutation.

addition by rearrow:
When procreating, each affinity has a 42% chance to be inherited from each parent and an 8% chance of mutating from each parent.

When an affinity mutates, it stays within a range of -3 to +3 of the parent's affinity.

Parent A has 8 power.
Parent B has 10 power.
Chances for kids' power:
42% 8
42% 10
8% 5-11, rerolled if higher than 10
8% 7-13, rerolled if higher than 10

Overall Affinity is the sum of all 5 affinities and determines the rarity.

For inheriting genes see