A parent/child relationship is crystal clear in the genetic data (barring the case where what you're actually seeing is an aunt or uncle and the child of their identical twin).
And I'm pretty sure paternity tests have a lot of precedent in US courts.
No, I mean that your identical twin's child will appear to be your child under a genetic test, for the obvious reason that you and your identical twin have the same genetics.
And I'm pretty sure paternity tests have a lot of precedent in US courts.