Surname Sieiro (Sieiro 
) , in the world, is quite a rare last name. The surname Sieiro is habitual in Panama, where it is quite a rare surname, Bahrain, and Portugal, where it is a rare surname. In absolute terms, it most frequently occurs in Brazil, Spain, and Argentina. Much less frequently, Sieiro is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Sieiro | Brazil, Spain, Mexico, Argentina, India |
| juan sieiro Spanish journalist, ES (b. 1835) |
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| arturo rodríguez sieiro Spanish politician, ES |
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| carmen sieiro researcher (ORCID 0000-0002-2475-4486) |
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| adrián sieiro Spanish canoeist, ES (b. 1992) |
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Mr, Luis, Luiz, Luna, Jair, Jade, Jose, Joao, Juan, Theo, Elio, Elsa, Erny, Hugo, Vera, Fran, Isis, Ilda, Ilma, Ieda, Olga, Maria, Leny, Gina, Gema, Gaby, Ms, Mã, Mª, Sol, Ana, Cã, Rui, Eva, Vã, Ivo, Mario, Ori, Sara, Alan, Anna, Caio, Paty, Raul, Rosa, Rita, Ryan, Diva, Marc, and Marta