We are all brothers

Twin towns or sister cities are agreements to promote commercial and cultural ties of different cities.

As in many other parts of the world, the Basque Country cities are joint with many others in the 5 continents. 

After a private guided tour I just made to a delegation, I investigated a bit on this subject and found this long list. Is your city amongst them?

Barakaldo
Cuba: Diez de Octubre
Ecuador: Portoviejo 
Sahara: Daira Burka-a Aaiun
Spain: Torredelcampo

Bayonne
Bulgaria: Veliko Tarnovo Велико Търново
Spain: Pamplone
United States of America: Daytona Beach, Florida & Bayonne, New Jersey

Biarritz
Argentina: Mar de Plata
Belgium: Ixelles
Morocco: Tétouan  تطاون, تطوان
Portugal: Cascais
Spain: Jerez de la Frontera & Zaragoza (Saragossa)
United States of America: Augusta, Georgia

Bilbao
Argentina: Buenos Aires and Rosario
China: Qingdao 青島市
Colombia: Medellín
France: Bordeaux
Georgia: Tiflis თბილისი
Spain: Sant Adrià de Besòs
United States of America: Pittsburg, Pennsylvania

Durango
Mexico: Durango

Estella
France: Saint-Jean-Pied-de-Port

Gernika
Germany: Pforzheim
Spain: Berga
United States of America: Boise, Idaho

Llodio
Nicaragua: Somoto
Sahara: Bou Craa بوكراع

Pamplona
Colombia: Pamplona
France: Bayonne
Germany: Paderborn
Japan: Yamaguchi 山口市
Poland: Toruń

Rentería
France: Tulle
Germany: Schondorf
Portugal: Lousada
Spain: Fuentepelayo & Monroy

Salvatierra
France: Bazas

Saint-Jean-Pied-de-Port
Spain: Estella

San Sebastián
Georgia: Batumi ბათუმი
Germany: Wiesbaden
Italy: Trento
Japan: Marugame 丸亀市
Mexico: Jiutepec
Sahara: Daira de Bojador الدائرة
United Kingdom: Plymouth
United States of America: Reno, Nevada

Vitoria-Gasteiz
Colombia: Ibagué
Brazil: Vitória
Equatorial Guinea: Cogo
France: Angoulême
Georgia: Kutaisi ქუთაისი
Peru: Sullana
Sahara: La Güera الكويرة & Zug
United States of America: Anaheim, California & Victoria, Texas

Zarautz
France: Pontarlier
Italy: Cardano al Campo
Sahara: Hagunia