Your oldest kid gets it, he is younger (will need the room longer) and lives there full-time.  The 17-year-old is only an EOWE visitor, and probably won't keep that up once he goes to college.

Please don't tell me your DH is insisting that his son get the biggest bedroom.  This one is a no-brainer. 

Very sorry about your first DH passing away.  Need more information.  IMHO, generally kids are not bent out of shape over size of bedrooms, unless there is a BIG difference.   I would ask, will 23 or 21 be visiting, is 21 in college.  If 23 or 21 will be visiting at times, you may want 17YO to be in room large enough that you can put two twin beds.

If the house is mostly for  your kids, you may want to consider separate fiances, if you are not doing that already.

I'd think carefully about how often the 17 year old will visit in the future. EOW won't happen. What is the holiday schedule now? Do you think that it will continue? Will he continue the two summer weeks? Or will jobs and internships preclude visits? 

Also DH has two older kids. What happened when they turned 18 or went off to college? Will this be what the 17 year old does? Do they visit? What are the arrangements for them?

The oldest of the kids who live there full time should get the biggest room.

I would give the largest rooms to the full time kids. 

We just moved at Christmas and have four bedrooms. Skids share the largest room, with its own bathroom. BS has his room and a play room. Skids bedroom is even larger than ours but I did not want to be in the basement. 

Youngest SS hardly visits so in no way was I going to have a room sit basically empty, especially when I’m at home with BS. 

Are your kids sharing, or will each of the 3 boys have his own room?  How big is the difference between rooms? I doubt I'd put the kid who is there EOWE and probably not even that much in a year or two in the biggest room absent some good reason to do so (such as that room being on a different floor).  In my family it was never a thing that the oldest got bigger or better things than the others, so that reason for giving the SS the biggest room holds no weight with me. But I wouldn't build a house with such a disparity in secondary bedrooms that it could cause a problem, either.

Should obviously get the largest master bedroom followed by the 12 year old and the 10-year old should get the same size bedroom as the guest bedroom which would be for guests and the 17 year old skid.  Assuming this is a 4 bedroom house.

Your oldes bio gets the biggest bedroom. He is using it more.  

It's your house, so it's your call. I say do what makes sense and works for the adults.

But...there is another approach...one that leverages social/group pressure to maybe get the result you want without you having to be the bad guy to make the call.

See, if someone offered me half a pie, I'd take it. But if they offered me half a pie and then told me 12 other people would have to share the other half, I could never take the half that's being offered to me. I'd feel guilty and my sense of practicality and fairness would overrule my stomach. I probably wouldn't even end up with one damn bite because I'd feel so guilty taking my part, let alone HALF THE DAMN PIE!

If your 17yo is mature enough, why not explain the pickle you're in deciding room assignments. Give him the fairness argument (he's oldest so he should get his choice) versus the practical one (but full-time kids would get more use out of the larger space than he would) -- and tell him and the other kids you're going to abide by his decision. Now he will be the bad guy...or the good guy, depending on how he chooses.

This way, if he ends up in the smaller room, it was HIS decision to give it up, not yours. But if he wants that bigger room in spite of what makes sense, make him say that and own it. That alone might guilt him into choosing the smaller room. But it will be HIS call to be greedy or gracious and in the end and you won't be the bad guy.

Either way, the younger kids will know this was 17yo's decision, so it will be on him to choose what's good for "the community" versus what's good for himself. If he chooses the bigger room, well, you were already considering giving him the larger room anyway, so nothing lost. But this way, you can tell the family it was 17yo's decision because he's oldest and he chose the larger room. Let the kids read the rest into it...you know they will!

i guess my first question is what are the living arrangements now? Who’s home do you all live in? What will happen to the home you have now? 

Is your current home where your kids grew up? If so, that’s a pretty big sacrifice to ask of them just to accommodate an EOWE visitor. First they lose their dad then they lose “home”? 

How about having a rule that the oldest kid gets the biggest room until he goes off to college?  Then during school breaks, the college kid gets one of the other rooms.

That way SS has the largest room for one year.  When he leaves for school, the 12 year old moves into that room.  

The kid who lives their full time

It is amazing what people fight about here.

Anyway, if it were me, I would simply base it on which children live there the most.  Disregarding relation to you or your DH, simply on who is there the most.  So I would give the 17 year old, who is there the least, the smallest room.  It makes no sense to have one of the larger rooms sat empty and unused majority of the year.

Before anyone goes nuts on this (basing it on age and relation) - I would do the same in my situation.  SS16 would get the bigger room as he lives with us full-time.  My own DS18 would get the smallest as he's only her a few weeks out of the year.

Suprised no one has suggested this yet but, if you are building the house then why not just make sure all the rooms are the same size? - There is probably some reason for differnet sized rooms, but it might be worth asking the question if it would be possible.

There are also other factors in play than the size of a room. The location of the room can also be important and may be more important to the kids than size. Is there a room that is away from the other bedrooms or that could have a separate entrance to the house that an older child might prize more. (No one wants to bring their girl/boy-friend home and share a joining wall with their parents or the living room). 

If you cannot build equal sized rooms then, I would offer up the discussion to the children. At the end of the day it makes little difference to you practically as to who has which room, and they may be able to come up with a solution between themselves that suits them all and saves you the stress. 

I am sure there are factors that you care about more when designing and building your own home. Focus on those and not irrelevant factors such as these. Remember also that the decision that you all come to is also not binding and if things do not work out the kids can move around at a later date. 

The oldest child that lives there full time. 

I mean really we complain all the time here that skids are catered to.  YET when a (what should be) simple room assignment question comes up...BOOM!!  End of the logical world that usually exists here.  What in the world???  When did kids become so precious that we have to first try and ask for the exact same size room?!  THEN if that can't happen then there's finances, feelings, logistics, size of the moon, blood relations, adults careers, ebb and flow of the ocean, school schedules and the Earth's rotation to take into consideration?!!!

When did small things become impossible things?  The size of the bedroom and home makes no difference to one's life.  It is the stability of the family/home environment, support, love, kindness and overall healthy environment that has the greatest impact.  The fact that your childhood bedroom was 8x9 or 14x16 will not make one blind bit of flipping difference.

Gawd sakes!

OP, there are only two posters in this thread who aren't agreeing with the rest of us that your oldest should get the better room, because he's there 24/7/365 to your stepson's 4 nights a month. 

The two posters who don't agree - one is not a stepparent, and the other is known for taking the contrary position from what everyone else thinks is logical. 

I don't really understand why your DH can't tell his son that it doesn't make sense for him to get the bigger room, but that you are building the house so he can have his own room, even it's smaller, and no longer have to push the 10 yo out of his room.

Stand firm with DH, your argument is the logical one.  Your SS17 will have his own room and it will still be his room when he goes to college.

So far this issue seems to only be an issue for the OP and her husband. We have not heard any indication that any of the children have a preference as to which room they get. As everyone pointed out the kids will all be fine in which ever room they end up in, so it really is just a case of the OP and her husband agreeing on something and this not becoming an issue to cause arguments between them. Any method of assigning rooms that achieves this is a good solution.

If you are building a home.. is there a way that the secondary rooms (not the master) could be similarly sized?  Also coming into play.. what is the arrangement of bathrooms etc.. a smaller room with it's own attached bath is more "valuable" than a larger plain vanilla room.  Are the rooms dramatically different in size? maybe is there a location that would be preferred.. even if it were a smaller room? 

There are lots of factors.  Theoretically... if no one is having to share the rooms.. I would tend to give the older full time kid a room of their own that is biggest and then work my way down with the part time resident having a smaller room.  They don't have as much "stuff" if they are just there part time.

Honestly I'm more concerned that this dream house has an open concept, a designated office space and a place for the kids to "hang out", oh and a specific room just for guests!
I've seen enough house hunters, love it or list it, etc. to know what you need to think of re-sale wise! Also please please please tell me that you are a work from home holistic cat healer and that your DH drives a bus for public transit and your budget is 2.5 million!
Sorry to be so toungue in cheek but I think we all needed a break.

OP has commented that the decision has been made since her original post. I totally agree with her and I probably would have LOL’d if my DH suggested drawing straws. 

My EOWE SD13 has the bigger of their rooms at our house, but it was just her, DH, and me when we moved in. We made sure that her room felt like her’s - painted her fav colors, let her pick out bedding, I even bought the bed! Her room is the most redone room in the house! She did know that her room had the potential to be used when guests (older sibs and relatives) came to visit, which isn’t very often. But that would have happened whether she was with us all the time or EOWE. As much as we’ve tried to make this feel like her room and her house, she still treats it as if she’s a guest. DH and I have a 3yo and now one on the way. SD asked if she’d have to switch to the smaller room. We don’t have plans for that right now but when she’s ready to go off to college, we’ll probably make the switch so the 2 younger ones share and she’ll still have her own (but smaller) room. 

And I will say, has anyone’s parents turned their room into a study, spare room, workout room, or sewing room the minute they left for college? My mom and stepdad didn’t, but I will say that I don’t think I fully unpacked when mom and I moved in with stepdad. Some of my stepsister’s stuff was still there (she’s older and wasn’t living there anymore) which we slowly moved elsewhere.