Family Bbqs

Because of COVID, we are having 2 separate BBQs (one for friends and one for family) so we can celebrate with people while still remaining in the number allowed for gatherings. The problem is that my FILs planned a BBQ at their house the weekend before with their family so that my fiance's brother who is flying into town could see everyone. I was fine with having that BBQ and even talked to my FMIL about having both theirs and ours, which she was fine with. Then I get a phone call from my FFIL who says that his family (which is most of the family that would be coming to our BBQ) might not want to go to both (which I understand) and that the brother won't be in town for our gathering (which I knew as well). The main problem for them is that there is only one that the brother can attend and it's the one that isn't our elopement party, which we obviously want our family to be at. My FMIL didn't tell him about our plans apparently and I already sent the invites for it to everyone. I simply assumed she would talk to him about it since they are married and live together in the same house. I just feel bad now because everything is a mess again. Thoughts?