Person recognition confusion.

My mom in law sometimes thinks her daughter is her (dead) sister. Other times she isn’t confused about it at all. Does your husband recognize you sometimes or never?

My mother stopped consistently recognizing me over 2 years ago, even in my own house. She sometimes argues with the care home’s staff when they introduce me as her daughter. Other times she calls me and even my husband by name, unprompted.

Very common. Sorry you are dealing with this. Just play along. Don't try to correct him as he really won't ever agree or understand. Maybe stop referring to yourself by name and instead as someone who cares for him? Heartbreaking, but no sense in upsetting and confusing him.

It sounds like your husband has capgras syndrome. You can "Google" it to see if it applies to your situation, but I'm betting it does.
I currently have 3 women in my caregiver support group whose husbands have capgras syndrome and believe they are 2 different wives with the same name or they don't know who they are at all and will threaten them.
Be vey careful as things can turn violent if your husband thinks you're someone else in his and his wife's Sandy's house.

Yes, as dementia progresses it is very common not to recognize who you are, or that you are related to him in any way. Some elders who enter MC form attachments to other residents, believing them to be "my daughter" or "my wife". It is common for husbands and wives visiting to be introduced to "my wife". Most, knowing this is simply the progression of the disease, are understanding. It is clearly a matter of loss upon loss, and I am so very sorry. This is very tough stuff.