FIL rang DP on Saturday and casually mentioned that the they are off on holiday this week with SIL and her DCs. AIBU to wonder why they hadn't mentioned it to us before? Or even invited us along?
Our DCs are similar in age, PIL and SIL live much closer to each other than we do but we try to make the effort to see them once a month/every six weeks. IMHO, this would have been a good opportunity for us to spend some more time with them all.