Cobblers' children are worst shod.

Basque 
Arotzaren extean keŕena zurez.
Translation: The craftsman has a bad roof.

Dutch
De baas woordt altijdt het slechtst bedient. 

Italian
In casa di calzolaio non si hanno scarpe.

German
Der schuster has die slechsten schue.

Polish
Swecz bez butow chodzi.

Portuguese
En casa de ferreiro o pior apeiro.

Romanian
Cizmarul umblă cu papucii rupţi.

Spanish
En casa del herrero, chuchillo de palo.