Can't reliably identify friends, family; mixes up family members
When it happens
Late in the moderate stage and into severe-stage dementia
Why it happens
Failing to recognize familiar people results from a progression of the brain's inability to connect various pieces of information. (Earlier in the disease, the person may mix up familiar names or faces or forget names and relationships -- but eventually all recognition may fade, sometimes even of the primary caregiver.) This can happen sporadically or continuously.
What you can do
Be patient. Not being recognized is a function of the disease, not a deliberate attempt to annoy you.
Try not to take it personally and gently remind others to do the same. Not being recognized is not a reflection of the quality or longevity of your relationship. It's not caused by not being close enough, loving enough, attentive enough. Eventually even spouses and children may be "forgotten."
Avoid quizzing the person: "Do you know who I am?" In this case, practice won't ever make perfect.
Identify yourself or the guest on approaching: "Hi, Mom. Look, your favorite niece, Melinda, is here to see you." "I'm back, Dad. It's Sam." Sometimes the person knows you're familiar, if not exactly who you are. "Placing" yourself"" can cause relief.
Correct mistakes gently if you like, but don't make a big deal out of doing so. The person with dementia may mistake you for someone long gone, such as a sibling or parent. You may choose to go along (no harm done) or to say, "No, it's your son, Bill. You've always said I look like Dad, haven't you?" But if being corrected upsets the person, let it go.