IRK, I’m with you here. It does irk me especially when dealing with professionals who are not supposed to be part of the uneducated masses. Such uneducated masses I generally avoid or ignore.
However, you didn’t explain why it is wrong. First graders are forgiven but adults are not excused.
As noted, it shouldn’t be “my grandmother took my brother and I fishing” because if you remove the other subject (the brother) and made it singular, it would be “my grandmother took me fishing” and that’s why “and I” is incorrect here.
As the GOAT, I take blame for not having the Grammar Police enforce. And I am sure my reply is also ridden with grammatical mistakes. But alas, as the GOAT, I am excused.
P.S. GOAT = Greatest Of All Time, not scapegoat LOL
Don’t get me started on “myself.” I get so many work emails that say something like “Please reply to Jane and myself by Friday.” I guess people think it sounds educated or sophisticated, but it doesn’t.