Totally unsurprising. It seemed a little too nice and wrapped up in a bow before, sometimes you just know who a person is. I’m glad you’re thinking about couples/pre-marital counseling – this isn’t going to be the last time his family gets in your relationship.
As for the wedding, I would say plan what you want and don’t tell the parents/sister until after it’s all over. Want to get married in Greece just the two of you? Do that! If you want to stay on the brunch wedding, the guest list overlap is small, so I think that should be on the table if it’s what you want.