Boyfriend [23M] is upset that I [21F] went on a vacation with my newly found siblings [24M/23F] without him.

Last year I found out that I have two half-siblings. We haven't been able to see much of each other because of the distance between us. But they invited me to go with them on a vacation to east Asia (South Korea and Japan) for two weeks. This was of course a sibling bonding experience for us since we didn't grow up together. I grew up as an only child and never thought I might have siblings. So this relationship with them is very valuable to me.
My boyfriend seemed upset that I was so excited about this and especially that I was going to spend two weeks with people who were effectively strangers (his words). He offered to pay his share and come with us but I didn't agree as this was a sibling thing. I offered to go somewhere else with him at a different time.
So I went and it was great. We really bonded well and we're now a lot closer. We're going to do more of this from now on to continuously strengthen our bond. My boyfriend keeps telling me this is weird and unnecessary and family isn't blood.
He's also upset that the three of us always stayed in the same hotel room. He thinks I should have had my own room since they weren't really that close to me. But isn't it the point of a bonding experience to spend as much time with each other as possible? Separate rooms would have defeated the purpose. A ton of our best moments happened because we were always together.
Is my boyfriend being crazy or did I do and am I doing something inappropriate and unreasonable?

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tl;dr: Boyfriend is upset that I went to a vacation without him. He thinks doing sibling bonding experiences with my newly found brother and sister doesn't make any sense since we are effectively strangers.


Source.