Why there is 份 in 身份?
In the past, it was 身分, which means the social position of an individual.

http://dict.revised.moe.edu.tw/cgi-bin/cbdic/gsweb.cgi?o=dcbdic&amp;searchid=Z00000131140

Somehow, in modern times, it evolved to 身份. Indeed, in Taiwan, the identity card is called "身分證", while in Hong Kong, it is called "身份證".

I would say that both "身分" &amp; "身份" have their supporters.

If you can read traditional Chinese characters, there's a pdf about the controversy over "分" or "份" in the translation of "identity card", by the law drafting division, Department of Justice, of Hong Kong.

http://www.cuhk.edu.hk/ics/clrc/crcl_48/yen.pdf

Have fun :)