Different Types of Double Buggies
If you’ve got twins, or two very young children who are seriously close in age, then you may be considering the option of a double pushchair of some kind. The basic choice is between buggies or double pushchairs that are either manufactured so the kids sit side-by-side, or they sit in tandem. Both work well, but people have different views about which is best. 
It is generally agreed tandem prams and buggies are most suitable for a baby and a toddler to share. This is because the back seat of most models reclines fully, but the front one doesn’t. When the seats are side-by-side, both recline fully, so the babes can both sleep comfortably at the same time. You’ll find a whole lot more information at Mumsnet and you can buy both types at eBay.