"This is leaning heavily on the assumption that your personality is primarily a product of your genetics"

Not really. If you allow that it is even 1% due to genetics, that better parenting compounds over generations. And there is a lot of evidence that it is much more than 1%. I too experienced numerous traumatic events by the time I was 12 and was then prone towards neuroticism for decades after. I still submit I'd be a much better parent to a clone than someone who has half my dna.