Sometimes I see people asking translation of words that can easily be found from a dictionary.
自己人is not one of those words to me. You cannot find an exact word with the same meaning in English. It goes a little deeper in Chinese culture.
One of the acceptable translations of自己人in English is “one of us”. However,to my understanding, there’s some tiny differences, hard to tell but not negligible.
I believe 自己人covers a smaller group of people than “one of us”. In other words, there is more exclusivity in 自己人.
You can be “one of us” if we live in the same community, or the same city, or the same country.
You can be “one of us” if we have similar background, or common understanding of living ways in the world.
But you can’t be 自己人if you don’t speak my language.
You can’t be 自己人if you don’t believe what I believe.
You can’t be 自己人if you don’t agree with my opinions.
You’ll be自己人when you have shared interests with me.
You’ll be自己人when you stand on my side, before trying to know if I am right or wrong.