Dear
@Mart2020
Welcome to DTP. Perhaps your wife has a brother and in her confusion she is seeing you as that person. Hope that makes sense.
I realise it hurts, my mum has asked me a few times who I am? Please accept it is just part of the Dementia experience, nothing we can do about it, just try not to let it upset us badly.
Please remember somewhere under the Dementia is your wife, who might be confused and muddled at times but needs you more than ever.
It would be best not to try and correct your wife. One of the volunteer moderators will no doubt reply to you soon, giving you a link to a thread about “compassionate communication”. Sorry my IT skills are to limited to give you the link. It helped me to work with mum in her confused moments, see the world how she does, respond in a helpful way within the muddled world of Dementia.