Unless the RAM is of the same latency it USUALLY will not work together. (I say usually, because some mobos may be able to arbitrate latency, but I have not seen reports of any).
Ideally, you should only use RAM from the same OEM with identical specs. I am afraid, jj, that you may not be able to use the RAM on a single mobo. My suggestion is to use it in another build, or sell one set and buy another set of RAM identical to the RAM you keep.