Visitor vs. tenant status for eviction

[Uwe K.]

So basically my question is:
When is a person in the rental a visitor, and when can he be considered a tenant?
My lease says visitors allowed up to 2 weeks. Pretty much standard here, and the same rule is in the statutes (WI).
Now I understand that there are many details that can influence it, but my background is, that the dad moved in with the daughter beg. of Jan. He also said he moved in until he finds a place on his own. He is not on the lease, I said he must be for Feb. if he stays, but agreed for him to be in there.
In the meantime I started the eviction because of non-payment, and I considered the dad to be a tenant and added him on the paper work.
They will try to deny that he was a tenant, so just wanted to hear your ideas and experiences. I think there was at least a verbal rental agreement between the dad and me. Just not sure now how the court will see it.
By the way, he used to live there before, was on the lease, but moved out. A new lease was signed with just the daughter at that point.