We live in a big city in Germany with two kids and earlier this year bought the Tern GSD mentioned in the article with two children seats. We don't own a car. This thing gets so much mileage it was definitely worth the money. Before, we frequently rented a car from a car sharing service when we had really bad weather or needed to drive a longer distance - we now pretty much NEVER rent a car anymore. The bike is absolutely lovely, feels very safe and is a joy to ride. It was a painfully expensive purchase, but very worth it.

When the kids get bigger we can exchange one of the seats with something comparable to a motorcycle back seat - a cushion and handlebars below the saddle - for the bigger kid. When they both grow out of it we can replace both seats with a chest or rack and have a very capable cargo bike. The whole bike is designed to not be much longer than a regular bike, so you can do pretty much everything you would usually be able to do, like putting it in a bike rack in the local trains and such. It also is built to be parked vertically due to support bars at the back tire (which, to be fair, doesn't work if you have two children seats, but still… nice feature).

I love it.