Let’s put it like this.
While I am not fully knowable of such laws in each state, I would, regardless of your state, strongly advise you not to shoot guests who have been invited into your home by you, or another member of the household.
Sorry, but a stranger in bed with my daughter is going to get a load of buckshot in the ass. What, I'm I going to quiz him 20 questions to find out his intent.
In the facts of the shooting we are discussing, it seems that the supposed invitee of the teen had entered in secret and in knowing disregard of the directives of the teen's mother, who was the homeowner and the adult head of household. For those reasons, and because statutory rape seems to have been intended or carried out, the claimed invitee would probably not be afforded protection as an exception to the "castle doctrine." And if he had become menacing when detected by the mother, the mother would be legally permitted to use deadly force to defend herself and her daughter without any duty to retreat.