In the mother of all modern-day pandemics, where separation is its own plague of sorts, there's another kind of sibling kinship that's been badly affected by border closures.
Unable to physically visit each other, the people of sister cities and towns across Australia and the world are resorting to alternative means to maintain their enduring, often profound friendships.
Take the case of Frankston, Victoria (population 145,985) and Susono, Japan (home to 53,740 people), whose sister city relationship, a kind of penpal-ship on a grand scale, turns an impressive 40 next year.
After a series of official delegation visits and events had to be cancelled, the two cities not unlike real siblings, have been connecting via regular Zoom video-conferencing meetings - some with gathered Japanese attendees wearing masks - as well as social media.
"It's been challenging and we've had to cancel quite a few events, including our annual Japanese Speech Contest and our planned visit to Susono in October," says Simon Hast, vice chairperson of the volunteer-based Frankston-Susono Friendship Association.
"Without boasting, we're one of the most active sister city organisations and we've actually been able to increase our contact during the pandemic."
The bond between of Frankston, 41 kilometres south-east of Melbourne, and Susono, 110 kilometres south-weat of Tokyo, is one of an estimated 560 sister city relationships in Australia. The main countries with which Australia shares such global friendship-based connections are, in order, Japan, China, the US, the UK and Italy.
Cities in other nations such as South Korea, Vietnam, Uganda, Kenya and Ghana are also looking for affiliations with Australia, according to Sister Cities Australia, an association of towns, shires, ports and cities which maintain a sister relationship.
The longest-standing sister city relationship in Australia is between Parkes, NSW and Coventry, UK, dating to 1939. The most recent to confirm a sister city relationship are Bundaberg, Queensland and Luganville, Vanuatu, formed only at the end of last month.
"Strong sister city relationships tend to have strong community involvement," says Mike Jakins, national secretary of Sister Cities Australia. "When this happens it is a wonderful way for both communities to learn about each other and appreciate their differences and similarities."
Although not officially sister cities, three other places, namely Bland, Dull and Boring, have evolved the concept to a new and exciting level.
They have created the League of Extraordinary Communities, a triumvirate of the Bland Shire, in the vast Riverina region of NSW, the tiny village of Dull, Scotland and the city of Boring, Oregon, in the US.
During the pandemic the three locations have been developing a "special passport" for when international travel can finally resume. Holders will be encouraged to get it stamped in all three locations, leading to a prize and entry into a League of Extraordinary Communities Hall of Fame.
Bland Shire's "far from Dull and Boring" initiative even won a coveted NSW Local Government Excellence Award for Creative Communities last year, with an art trail which includes a special League of Extraordinary Communities selfie sign to mark the association with Dull and Boring.
"Council sensed an opportunity to transform what some may have perceived as a negative by transforming the name of our Shire into a positive globally recognised destination," says Ray Smith, general manager of Bland Shire, who has visited Dull and hopes to also take a Boring trip, as it were, before retirement.
Back in a frankly more serious-minded Frankston (which also enjoys a sister city relationship with Wuxi in eastern China), mayor Kris Bolam says they have a memorandum of understanding to establish a friendship city relationship with the Fijian capital of Suva, as well as discussions underway to form another with Frankston, Texas.
The existing sister city associations have led to the creation of a "Wuxi Way", a "Susono Way" and two Japanese gardens created as lasting monuments to the friendships. Talk about a sister act.