I'm confused about the persons in this drama. A "boyfriend" seems to appear about halfway through your facts. Are you saying that your daughter has a boyfriend in addition to your son-in-law? Or have you just started referring to your co-owner son-in-law as a boyfriend?

In any event, the basic rule of law is that all co-owners have the right to possess the entire co-owned parcel. Therefore, you cannot evict your son-in-law, and you probably cannot evict anyone to whom he has given possession, such as his wife, nor probably their guests.

There is a possible exception if you have been "ousted" from co-possession, but I don't think it is applicable here, since you were never a co-owner in possession. However, you might want to look up and read Civil Code section 843 to see if it fits your facts. Probably not.

The standard remedy for an unhappy co-owner is a special kind of lawsuit called a partition action. This action asks a court to order the property sold, after which the net proceeds of sale are divided among the former co-owners in proportion to their interests and after adjustments for excess costs borne by a party for mortgage, taxes, insurance, etc. Before undertaking a partition suit in today's real-estate market, a prospective plaintiff should look at the economics carefully!

Finally, if there is suspected criminal activity, I am a little rusty in that area of the law. I know that if the offenders were your tenants, you would have a right to evict, but these are not tenants of yours. If there are situations that might affect public health or safety, you might contact the district attorney or the police for advice.

You may threaten a partition action which would force sale of the house. Contact me directly.