it is a good point that he doesn’t celebrate Christmas anyway so it’s not like it matters to him
To be fair, I don't celebrate easter, but being invited to a Greek family easter was a lovely experience. The friend I was staying with hosted me though - we attended church, popped in & out of family homes for quick drinks & introductions, chatted to people promenading - but SHE was the person making herself responsible for me. It wouldn't have occurred to her to foist me off on someone else so she wouldn't have to cater for me.
I'd have been surprised if she'd told me "I can't be arsed to show you easter traditions myself so will mooch off my brother & we'll game instead of joining in & having fun with the kids. Oh dear - he wasn't expecting you & is only having close family today, so instead of doing my own easter I'm going to badger him until he relents. Ooops he isn't relenting, oh well that's YOU dumped then."
I'd have coped perfectly fine but been a bit
. At her. Not her brother. He wasn't my host.
But she's not like OP's brother. Being dual nationality herself she knows how overwhelming & knackering performing "foreign guest who speaks Greek like a 2 year old" & "doesn't know us or understand our customs but appreciates being briefly introduced" all day is. So she ensured I got the best of both worlds - see & dip into the experience, but be whisked off back to the social comfort of her own home to deal with our own lamb pit & talk English like loons (she missed her first language).
Not an iota of this has occurred to OP's brother.
He didn't plan for his guest's comfort because he didn't expect to have to.
he thought he could dump it all on OP, & rock up with a (maybe shy, as are many visitors, even if fluent) pal & sit on his arse gaming all day at her house while not contributing a jot.