In 1944, Coventry and Volgograd created the first twin cities whose aim was to promote peace and reconciliation between people in different countries. However, what we now call twin cities have existed for over 1000 years (see the Wikipedia article on Sister Cities below).
Coventry is now twinned with 26 other cities. However, the participation by and awareness of most citizens is extremely limited. As an article in The Guardian said in 2011,
town twinning must evolve if it’s to remain relevant – and not be just a holiday perk for local dignitaries.
Indeed, Wikipedia, which regards the term Twin Cities as being:
a special case of two cities or urban centres that are founded in close geographic proximity and then grow into each other over time, losing most of their mutual buffer zone.
What we here call twin cities, they call Sister Cities