4allweknow
What's the point in having more than one PoA if only one signature is required to officially carry out the terms. Surely if there is more than one all must agree any decision. Can understand if urgent decisions needed and distance is involved but with all the technoligy available now signatures etc can be transferred almost immediately.
You can set them up how you choose. Our two children both have POA, but either of them can sign things off. We chose to do it that way, although you can set it so they both need to do it.
Unless they live next door to one another, and you can be sure that this will continue, however, it's probably not the best idea. Part of the point of financial POA is so that if, say we were both abroad and needed money to pay medical bills, get a flight home, or get out of jail (!!) they can access it. In those circumstances we'd want action taken as close to immediately as possible, not to have to wait until one could get to the other so they could both sign a document.