Originally Posted by AsiaTraveler

Most rolling bags have connectors available these days. It's not pretty, but I've used those to chain bags together and get to the bag check ​​​​​before. I think I've personally moved 4 bags that way when my kids were small.

Some non-rolling carry-ons also have a flap/slot on the back where you can slide it over the handle of a rolling suitcase.