When bro is such a bro you completely forget he's trans.
My wife's got a friend this happens with all the time. She'll be talking to him and something about our oldest will come up. She'll make some remark to him thinking he'll relate, entirely forgetting that he had to transition so he didn't experience whatever it was the same way.
This reminds me of a burn my wife gave to a random guy that decided to hit on her one day she was out running errands while I was taking care of the kids.
Deadass just first thing out of her mouth after he hit her with the "I won't tell if you won't," to her saying she's married. "Ew, I'm gonna need you to tell me what about any of this (gesturing to her entire Butch Lesbian look) made you believe I was straight so I can immediately remedy it." I almost felt bad for the guy for a second. Almost.