Sorry for the throwaway, ladies. I comment here a lot and don’t care to air my dirty laundry on my known account.

I live with my fiancé. 30s, few years together, childhood friends. He has split custody of his son. We are preparing for the long, multi-state drive to pick him up. He had previously asked if we could bring his ex’s oldest (18, m) back with us and drop him off to stay with a friend for the summer. I agreed, as it was on the way.

He came home tonight and said there might be a problem with the oldest son coming to visit. The family he’s supposed to stay with will be taking a trip out of state for a month and a half. He asked how I felt about him staying with us for that time. I didn’t say anything for a moment and he asked, “Well, do you want to drive him all the way back to [state] halfway through the summer?” I said no, as I hate long road trips.

The truth is I’m not comfortable being responsible for someone’s adult kid. I’ve only met him two or three times and he hardly spoke. I don’t know if my fiancé factored in how much more we’ll need to spend on food, utilities, or entertainment. I don’t think he’s realized that I’ll have double the amount of laundry, dishes, and food to cook all while his day doesn’t change at work. And honestly what am I to do if the son gets up and leaves while I’m the only one home with him? I can’t stop him. It’s concerning.

The other thing (that I may be taking the wrong way) is the way my fiancé posed the alternative, implying I would have to take a multi-day trip and drive the oldest back home. I don’t mean to be snarky, but I fail to see how it’s my responsibility to return an adult man across the country to his mother.

My other fear is if I say no, the ex will spitefully prevent the son from seeing his dad. She already has.

I think I appeared uncomfortable because my fiancé stopped talking and told me just to think about it. I didn’t raise any concerns at the time because STFU.

I don’t want to be negative, but this seems like an unreasonable request. If there’s another way to look at this I’m open to any and all advice. I’d like to be supportive but this feels way out of my comfort zone.