What can I do with people are living in my property

[Lynne Garris]

Okay hello...I have this friend he has this property that he owns yet there is a situation where people think they own it. They think they bought this house but they actually

Bought lot next door. The realetor messed up majorly but selling them the wrong lot. They have been there 3 years which my friend owns it. What he can do? Also he had a surveyor, they showed him that he owns it not them. Please help.