Am I overthinking this and what should I say to them?

I’ve been messing around with a guy for 3 years sneaking around. For his 21st birthday he invited me to Europe with him, but also I’m meeting his family (both his parents, 18 year old sister and older brother). I’m really nervous meeting them and what to say, because of past experience with my ex bf’s family traumatizing me.

Am I overthinking this and what should I say to them?
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