I have no idea how reliable the Twingo is, as we have very little for affordable European cars here in Canada, but the Renault Twingo and the Smart Forfour are twins built at the same plant and share 70% of each other's parts.
Neat!
Similar arrangement for the Peugeot 108 / Toyota Aygo / Citroen C1.
VW has the Up!/SEAT Mii/Skoda Citigo, but that makes sense as they do that with most of their cars in Europe.
Makes sense... less profitable so if you share the development costs with a few companies or brands, it makes it more profitable for everyone.