The Hauck Duett is a stroller with a 2in1 pramette seat that can be used for a single child or in a tandem configuration suitable for two children. It was released in 2011. You can convert the main seat into a carrycot (and vice versa) by simply unfastening the buckles. It can be tilted to a fully reclined position. The stroller comes with the included second seat which, when attached, is oriented into the shopping basket. You can also recline it, but only partially. When both seats are attached, they can face only forward. The main seat is reversible only in the single mode.
The Duett, due to the different seats and the possibility to attach only one car seat, is suitable for a younger and an older sibling. You can use it for twins, but only when at least one of them is able to sit independently.