Family name Си-Ин (Си-Ин 
) , worldwide, is an extremely rare surname. The last name Си-Ин is characteristic of Central Asia, particularly Kazakhstan, where it is a very rare surname. Also, Си-Ин is the forename as well as the last name. Parts of the name also exists independently as a first name Си, and a first name Ин.
| VARIANT | COUNTRY |
|---|---|
| Си-Ин | Kazakhstan |