My Wife undresses in front of her twin brother  

My wife’s twin brother happens to be managing me and my partner but his stay is currently causing us problems as my partner keeps changing her clothes before him. She’s never completely naked before him but she does not have any reservations in taking her fill up and speaking with him in her bra. She says they’re very close, that there’s nothing she’s hiding from her brother, forgetting she is really a married woman. I’ve tried to let her understand my position but she says I’m creating a big deal out of nothing. I must say i creating a big deal doing this or it this really a big deal and something I should be worried about ?