I don't know how closely you've followed the trans threads on here, Mama, but one recurring theme is how much the extreme transactivist position relies on "appropriation", or stealing other people's experiences and making them your own (transactivists as opposed to old-school transsexuals trying to deal with bodily dysphoria as best they can - people towards whom I think many of us feel a lot of sympathy. I quite like the analogy that old-school transsexuals come to womanhood as refugees, transactivists come to womanhood as colonisers.)
So, the most obvious one is appropriating women's biology (the claim that they are literally female).
Also appropriating sexual stereotypes, and turning them from something we women have spent our whole lives fighting against into something "desirable", something that marks you out as "womanly" (see for instance Paris Lees writing about being cat-called in the street, or Jane Fae on women's hour talking about unshaven legs as "dirty").
But also - appropriating intersex conditions (to muddy the waters over the "literally women" issue by trying to make out that biological sex is fearfully complicated and not well understood).
Or - appropriating the black civil rights movement in America by claiming that women wanting to keep male-bodied part-time cross-dressers like Travis Ablanza out of women's spaces (spaces we need to escape from male harassment, not as a way of trying to set ourselves up as "better than men") is like white people excluding black people from the front seats of the bus.
The whole movement is like a rendition of Pulp's Common People on continuous loop.
Unfortunately your relative has become the latest piece of collateral damage in this project.