I promise not to let this degenerate into one of my whines about step kids. Just humor me.
Let's have a hypothetical...18 yo young adult children. Living in your home in anticipation of going off to college next fall. You provide room, board, etc. You will be helping pay for their college education so long as they are performing reasonably well. They are high school seniors, reasonably responsible, have part time jobs that they save and use for their discretionary spending, pay for their gas, insurance, etc.
At 18 and living in your home I think you certainly have a say as to reasonable hours to be in, quiet enjoyment of the house by all living there, etc.
But what about their comings and goings?
Should they be allowed to have spend the night company of the opposite sex in your/their home?
Should they be allowed to spend the night with their bf/gf's away from your home at the bf/gf's house?
Should they be allowed to go away for weeekends with bf/gf's so long as they tell you where they are going to be?
If they are making such "adult" decisions unilaterally and not actually asking for your permission but rather merely informing you of their whereabouts/actions so you will know what is going on, is it time for them to assume adult responsibilities such as gettting there own apartments/pay rent/pay for their own food, etc?
Would your answer change depending on the gender of the child?
Should they be allowed to come and go as they please so long as they keep you informed?