[muskstinks]

You need to find a genome change if it exists which requires whole genome sequencing. so its a money question and doesn't guarantee a result

[giantg2]

And even if a genome change exists, it may not show up in the offspring depending on which version of gamete they're derived from.

[GeekyBear]

With identical twins, the genome is identical since both twins derive from the same fertilized egg.

I'm not sure how future advancements can overcome that issue.

[muskstinks]

There can be very small mutation which you might be able to find if it happened.