>>213444166
>their understanding of genetics is stuck to late 90s for convenience of the masters
Ironic of you to say that.

Chromosomes exchange genetic material during meiosis, meaning that in your example, the children wouldn't have XXXXXYYYYY, or XYXYXYXYXY, instead they both would have X-ish Ys and Y-ish Xs.

In summary, the chromosomes you got from your paternal grandparents will exchange genes with the chromosomes you got from your maternal grandparents, even though your paternal grandparents didn't reproduce with your maternal grandparents.