Not the same numbers but I just combined four 3 week old chicks with ten 1 day old chicks with no problem. I think they would be ok but if you try it, watch them closely for an hour or so to make sure the eldest doesn't beat them up. I am willing to bet it will be fine though. The older one will probably peck a little at their egg tooth at the end of their beaks but still, should be fine. Good luck and post your results, please!