When you do a DNA test and submit your results, you might be able to find people you're related to. People you didn't know about before.
The graphical essay linked above outlines some of the history of racism at the foundation of our country. Genealogy efforts are orders of magnitude more difficult in the US if you're not a descendant of white European folk. This is adequately explained by those white Europeans' need to erase the humanity of African slaves and North American indigenous residents.
Popularized DNA testing is a pretty fraught undertaking, even if your ethnicity is well-represented in their datasets. You can find, in the last ten or fifteen years of advice columns, dozens of letters about heretofore unrevealed infidelities and small-town couples that just learned they are (oopsies!) incestuous. All brought to our attention thanks to 23&Me or similar.
There's even a rather mild instance of this in my own family. My brother did a test and was notified that he had a cousin on our father's side, living just a few miles from him. Which made no sense at first, because he's the only member of our family who lives in Florida.
Sure enough: it turned out that our zaydie was, as we would say back in the day, "a bit of a hound dawg". The reason he and our bubbie split back when my dad was quite young was, Zaydie had not quite fulfilled the requirement of divorcing his first wife before he married his second (who was our bubbie). From there he went on to further his colorful career as a Lothario, finishing up with swindling an ingenue out of $7,300 in money and jewels (over $146,200 in 2021 dollars). This earned him the privilege of becoming a guest of the State of New York for quite a few months at their well-known accommodation: Sing-Sing.
This heretofore unknown cousin my brother found turned out to be offspring from my zaydie's first marriage. Their conversations led us to learn of dozens more of our relatives scattered all over the East Coast and Midwest.
I guess I am thankful that the revelations that came to me and my family from my brother's recreational genetic testing were not more traumatic. This is something to consider before you buy your whole family spit kits for a Christmas gift.