This is insane.
Can I ask, is there anything else that could possibly be done here to make the life of the ALMIGHTY KING OF THE HOME any easier? Because I am concerned here that all the serfs - which here translates as the underfoot, non-penis-owning SCUM - may actually be enjoying some of the comfort which by all rights should be his. You say there are three bedrooms, for example? Could you and your DD not permanently share the smallest, so that THE ALMIGHTY KING could e.g. have somewhere nice to put his luggage when he graces you with his presence?
(I hope the above has outlined my likely approach to the problem)
Ok. So:
You have three bedrooms.
The biggest bedroom and the huge expanse of bed is permanently reserved for the person who is present the least and who is never expected to share his room. Obviously, this is the ALMIGHTY PENIS KING!KING!KING!
The ?second biggest is used by the child who lives there permanently.
The smallest goes to the ScumSlave (i.e., the woman of the home :) )
When there are visitors - the King lies undisturbed. The women bunk together. In the second largest room? Oh no. The visitors have that. The women of the home spend uncomfortable nights.
The visitors are actually the primary 'responsibility' of the King, but that means nothing. There is compromise to be made; ergo, that is the woman's territory.
The child of the home could share the biggest bed with their other parent (logical) - but that would disturb the King. That can't happen.
And now - a discussion of how more people could be squeezed into the house.
How can you even begin to justify the setup you HAVE, let alone even try and begin a discussion about his sons moving in?
Here's the conversation I suggest you have. If you can't have this conversation, ask yourself why.
'DH, I've been thinking about this issue of YOUR sons having a place here, albeit technically, right now. I think it's right that they do. How we would do that has got me thinking along how badly, inefficiently and UNFAIRLY the rooms are working at the moment. So we need to change and allocate rooms firstly by need and frequency of use, and secondly by personal preferences.
'Firstly, we need to swap rooms. I'm here all the time, you're here much less frequently. I use my room more than you. Secondly, I'm the one having DD bunk in with me when your sons are here. She's getting bigger, and also if there's a possibility that they're going to be here more, the biggest room needs to be given over to that most intensive use: me every night, DD with me possibly quite a lot and possibly even permanently. I need that room and that bed.
'You have expressed a preference to not have to share, ever. If we can accommodate that, you can see that you'll be the ONLY person in the home with that luxury. The other four people will have to share two rooms. There is no argument that can say it's fair that you get the use of ANYTHING but the smallest room.
'With this swap, it makes it at least doable for your boys to, in theory, come and stay. DD keeps her middle-sized room for now, and if they need to come and stay, they have that room and DD can move in with me. Not ideal, but doable.
'If only one of the boys comes to stay, we should probably have a conversation about aranging things differently - DD in with me with one other child, who is older and doesn't use the room space in the same way, having a room to himself might end up being quite unfair on her. In that scenario, you and your son sharing the biggest room, me in the small and DD in her room might be best.
'We will start moving things around this weekend.'