P.B.
Give him "positive" instead of negative: rather than say: "We are NOT going to live together anymore" (or however you want to put it, it's still something yoiu are not going to have anymore), tell him that he's going to still enjoy mommy and daddy and that he' s going to have 2 houses and 2 bedrooms all for himself.Tell him that whenever he wants to talk to or see one either one of you (parents) while he's at either one's home, you both will call him or go see him.When asked "why", simply tell him that sometimes parents need to have two different homes (don't use psychologically heavy words as "separate") and that he'll get to pick his new furniture/toys/decor/etc... 5 is too young to be able to grasp the adult explanations of divorce, make clear his home arrangements are going to change by higlighting the "positive" things (although positive is not a word that makes sense in divorce, but he still needs to perceive some things as positive), don't talk to him as it was a big deal but still prepare him to transition into the change. More details can be shared later, for now the most important thing is to help him minimize the stress of the change and adjust to the different homes and to not having one of you with him at all times. Keep it simple, still telling the thruth, but avoid instilling tension or sadness or any other negative feeling you may project on him while breaking "the news". Remember he is not an adult, he does not need too much information: just what matters to him. Good luck.