Are you storing other people’s items in your home?  People who don’t actually live there? 
… a grown child’s toys and memorabilia
… your brother’s furniture that doesn’t fit in his current home
… clothes or tools you borrowed from a friend
… items you inherited from deceased family members
… your great aunt’s furniture that you really don’t like
 
Working as a professional organizer, I find that many people do have other people’s belongings stored in their home.  The reasons are vast and varied.   (Link to Part 1: Your Home is Not a Storage Unit.)
 
There’s nothing necessarily wrong with having other people’s items in your home. But if you feel resentful about it, it may be time to take a closer look at why: 

​KonMari tackles sentimental items (such as photos, memorabilia, heirlooms, etc.) as the last category of the tidying festival, because when you reach to this point you have already honed your spark joy sensibility and are in a better position to decide whether an item will serve a good purpose in your life. By the time I did my tidying festival -I have to be honest- I didn’t check these cassettes (shame on me! I know) but mainly because I had forgotten they even existed and because they were not 100% mine, they were my whole family’s.