Have twins? Or maybe you are babysitting? There are definitely times when the tandem carry comes in handy to carry two babies. When my daughter was about nine months old, I used to babysit an older baby, about 18 months. We lived upstairs and I often would put my daughter in a front baby carrier and the older baby on my back to go up and down the stairs and go for walks. Just keep in mind that the baby on your back needs to be able to sit up on her own before you can attempt the back carry. Also...practice the back carry itself before you try tandem carrying! This is not your beginner carry, but once you master the back carry, it's a great tool to have in your parenting tool kit!