Twin towns and sister cities are two of many terms used to describe the cooperative agreements between towns, cities and even counties in geographically and politically distinct areas to promote cultural and commercial ties.
We have a Caln Township near where I live and it is "twinned" with Calne, England (Anywhere near you by any chance? That would be a VERY curious coincidence!!!!)
the help out kinda they support each other like scotland it twinned with Malawi and every year we do a special collection for malawi it;s almost like family
There is another town somewhere else that is of similar size and makeup. So as a promotional gimmick they call themselves "twins" and make up all kinds of stupid comparisons and competitions.
I lived in Fort Smith, Arkansas for many years and it was sister cities with Cisterna, Italy (there was a sign). I knew they were sister cities because a particular WWII battle (Battle of Cisterna, outside of Cisterna, Italy) was lead by a guy from Fort Smith. But I had no idea what the heck it meant that they were sister cities.