If you want your mind-blown, read up on feto-maternal microchimerism:

https://pmc.ncbi.nlm.nih.gov/articles/PMC8762399/

tl;dr: All boy moms will have some proportion of XY cells lodged in their bodies until they die. And this can result in them showing up as genetically male on a DNA test, simply because they once gave birth to a boy. When you get down to a cellular or molecular level, notions of "sex" or even "individuality" are far more blurry than our mental models admit. Sorta like recent findings that by cell count, humans are only about 43% human, and the rest is the bacteria making up our microbiome, and that our microbiome can have significant impact on our behavior.

https://www.bbc.com/news/health-43674270