He is now denying the validity of dna tests. I don’t want to say the past 35 years of having him treat me worse than he treats his sister had anything to do with his assumptions of my dna, but he was upset to learn that I am more Irish than him. I wonder what he thought of my mother before these results…
It's unstated racism.
If someone in your past could get a good tan, it was common to say that they were part "< insert native american tribe from your area>" because you definitely didn't want to be perceived as part black.
Look up the "one-drop rule".
I'm sure that was a factor in many of these instances. That said in our family my impression was it was more of a "here's something special about us" type thing, like there's nothing otherwise noteworthy.
That's generally how these things are always communicated to later generations. 😂