How can my full sister and I only share about 21% ethinticity? I am 79.6% N and W European and 20.4% English. She shows being only 0.9% N and W European and 65.4% English. She has 3 other regions also that don't show up for me at all.
Easy. Siblings don't share 100% of the same ethnicity. Recombination is quite a random thing and never repeats. They may not share some of the things. Kids have different %, some of them may not inherit ethnicity which their siblings did.
Here it is quite an easy explanation of recombination (on lego): https://youtu.be/-f7VUPmgy2U