I was hoping that somebody had already invented a device that makes two individual strollers seem like double strollers. Why is this a concern to me? For our upcoming trip, I don't think we'll be bringing a yaya. In addition to that, we already have three strollers and we don't want to purchase another one. Since it'll be just Vic and me tending to the kids full-time, I'd like us to be more mobile, with our hands free for other things. Besides, I think Javi and Bettina would rather sit than walk all the time. With some carefully chosen words, I found what I needed in Google. There are two available in the market. Here's something from Prince Lionheart. Amazon sells this at $13.49. Here's the one from Munchkin. This costs around $9, shipping not included. Both come in threes, to be attached at the top and bottom frames. I am just not sure which is more sturdy. Luckily, I don't have to purchase these from Amazon....