Partner is very close to cousins particularly one close in age. We see him and his partner about 3 or 4 times a year travelling to their country and them coming to us.
Partner’s brother left his wife a few years ago- kids grown-amicable as can be nobody else’s involved.
At the cousin’s wedding last year We met BiL’s new partner for the first time. Lovely woman and good company. Met her about 3 times since all good.
When at cousin’s an invitation arrived for them for her significant birthday party, we invited them to stay with us when they came for party but we are not invited. Partner told his brother and he said she wanted to invite them as they had included her in wedding even though she was new to family and they had never met her, they don’t live together. Partner annoyed as it will be embarrassing. He is driving cousin who is staying with us to his own brother’s partner’s party but we’re not invited. I know we don’t really know her but we have met her and got on. I feel that it will be really awkward and putting cousins in an embarrassing position.