My mum told me out of the blue that she is adopted and that my grandparents who I love dearly are not biologically related.
She didn't mean to tell me, and only let it slip during an argument. I also think her mental health was not at a good place at the time.
Not sure if she made it up or not, and cannot check with anyone else as no one who is still around would know. Feeling very confused and somewhat angry that this was kept from me all this time. AIBU?