stranger in my house

I have had a stranger living in my house for quite sometime. I never see them but I see evidence!!
At first I thought it was the ghost of the woman who died in my house. BUT she was a mother of two boys just like me. She seemed to be organized and strict (neighbor stories) like me. SOOO because of the nature of the evidence, I don't think it is the ghost of the woman.

The boys have more information about this stranger than I do. They know its name....Knotmae

Here is the evidence:
Me: "who left the bathroom light on?" (which means the exhaust fan is also running)
boys: "Knotmae!"
Me: "who left the back door open?"
boys: "Knotmae!"
Me: "who left the lego room door open?" (which means the dog can get to the legos and eat them)
boys: "Knotmae!"
Me: "who didn't wash their dishes?"
boys: "Knotmae!"

I will catch this Knotmae one day!!!