Family name Sidej (Sidej 
, Сидей 
) , around the world, is a rare cognomen. The surname Sidej is habitual in Eastern Europe, particularly Czechia, where it is a rare surname, Russia, and Ukraine, where it is a very rare surname. Much less frequently, Sidej is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Sidej | India, Czechia |
| Сидей | Russia, Ukraine |
| nikolaj sidej UA (b. 1916) |
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| vasil sidej UA (b. 1918) |
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| nikolaj sidej UA (b. 1920) |
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| richard sidej CZ (b. 1972) |
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