If you are looking for a real answer to the situation, consult a lawyer.
What I personally would do is have each tenant sign a 12-month lease agreement. This establishes they owe rent, utilities, whatever you decide to collect. You (of course, that means the landlord) then can use that money for repairs, taxes, utilities, mortgage, profit and so forth. This becomes a business and therefore brings some income tax issues. Operating costs lower income (less tax) and rents increase revenue (more tax). If you take in $10,000 of rent money this year, and spend $20,000 fixing up the house, you reduce your personal taxable income by the extra $10,000 in operational expenses. You can also reduce personal taxes by writing off the depreciation of the property.
Once the landlord/tenant relationship is defined, eviction is done by following the law, and you can have the court and LE help.
Keeping it as "relatives living as a family" muddies the water. Technically, unless their names are on the title, they have no claim of ownership. However, as macsak said, the courts probably see them as tenants (albeit freeloading tenants). You may still have to follow the eviction process to avoid lawsuits.
One other solution to consider. Sell the house to another party, hire a rental manager, and then it's purely a business arrangement, not a personal family situation.
Just thinking out loud... wish you luck!