The other is that he should have consulted you before his son moved in. This is where some pps (including me) are saying you're at least a bit unreasonable. It's an issue of expectations and communication. Ywbu by never having considered the possibility of him moving in.
As the same person as the OP in my own situation, I have to point out that, no, we (partners of people with adult children) shouldn't/don't consider those possibilities, because we wouldn't expect the same "automatic" reaction the other way.
When my ex moved in, his adult child had been living in the same place for years, with no mention of ever moving away (long distance from us). Their relationship had been based on him travelling there and a lot of phone/facetime contact.
Years of this later, he suddenly announced that he wanted adult child to move into our very small house on an ad-hoc, at their pleasure, free of charge basis. No discussion, no "I have been thinking this...", no "how could this work...". just him saying "I want this so it will happen".
No consideration given to the fact my study (used daily) would turn into a permanent spare room; no consideration given to the fact he worked away a lot and I'd be left hosting a near-stranger who didn't drive, have any local friends, know the area etc. No consideration of the extra pressures on us by suddenly having a third person there all the time.
And yet, my ex found this completely unreasonable of ME!
(In comparison, if I was thinking of inviting people to visit, I would check with ex regarding any existing plans and arrange accordingly. I wouldn't dream of just arranging a visit from my brother without telling ex, it's just rude).