What if you want to move not one but more persons on a bike?
With children there are more ways to do that. One child on the back, or a child in a seat on the front. On the handlebar, or on the frame.
But what if you want to take two children with you on the back of your bike?
On the road, we came a long this bike. With a longer rearend of the bike. More room for the twins.