How would you feel if your spouse of three years stayed overnight with her ex-husband, who was diagnosed with mild cognitive impairment?  They were previously married (twice) to each other.  She is helping him with all his affairs and staying at the house,  because he has short term memory problems, yet he still drives, cooks and functions well.  I understand that he is like family to her, but it leaves me feeling uncomfortable.  

Your thoughts are appreciated.