Eviction of adult family members

Unless they are paying rent, they do not have a right to remain in your home; they should simply be guests, and you should simply be able to ask them to leave. (And  to call the police for assistance if they refuse to.)

However, if the sheriff will not help you and believes you need to go through eviction, it might be best to do so--the process is fairly streamlined and inexpensive. It will take a couple of weeks, but if that gets the sheriff to help you, you may be worth it.

Assuming that they do not (and never have paid rent/utilities), they will be considered to be  "licensees"; that is they entered and remained on the premises with permission.  Now that such permission has been revoked the lawful way to remove them from the premises is to serve them with a notice to quit (under these circumstances in some states this notice can be for a little as 3 days, in other as much as 30 days).  If they fails to leave at the end of that time you will have to go through the requisite procedures for eviction in your state.  At this stage the police will be most probably refuse to get involved.  Once the court enters an order for the tenant to vacate the property it will be enforced by the sheriff, using physical force if necessary.

What you need to do now is to speak with an attorney in your area.  They will advise you on the correct procedures for all of this.  If you fail to comply with these procedures you could find yourself on the receiving end of a lawsuit for unlawful eviction.