Downstairs is Always cold

I have radiator heat. It runs on fuel oil, but I think water is in the actual radiator. My house is very open to inside airflow except upstairs. My brother in-law's room is small and gets very hot. He covers his radiator with a sheet/blanket but doesn't close his bedroom door that is at the very top of the stairs and sometimes opens his window to cool down but shuts the door while the window is open, then opens the door again right after he closes the window. Rather than leave the door shut and keep the cold air in his room, he opens the door, letting all that cold air rush downstairs right by the thermostat, kicking the furnace on. I'm convinced this is wasting my fuel and the heat in my house.
Another situation is my Father in-Law's bedroom is just a few steps down the hall from his room. He Leaves his door shut all the time with a rolled blanket in front of the door. But he still has his window a/c in the window but swears he is only running it on fan. ( It's 2degrees F this morning where I live.)He claims his room gets hot also. How much fuel and heat is being wasted from him not opening his door to flow that hot air down into the rest of the house? How much energy is he wasting leaving the a/c window unit in and running it on fan 24/7?
My bedroom is at the very end of the hall almost directly across from my Father-in-law. My room gets warm and sometimes hot. I don't block my radiator, and use a fan near my door to push the hot air into the hall and downstairs. It does help.
Am I nuts thinking that since they are blocking the heat from their rooms, then the Heat that is being pushed to those radiators is being wasted instead of being pushed through the rest of the house? Am I wasting money on fuel? Am I cold as hell downstairs b/c they aren't sharing their heat from their radiators?
Side Note : We did contact our Fuel supplier and got a quote to remove the radiators in those rooms, but it was gonna be $ each.