I think you have a point.  I wouldn't be thrilled to have him all summer. I'd be afraid the parents would show up for an extended visit too.

If he's out of school and can't stay on campus, I'm going to assume he's in college and going back in the fall. If he's in college he should be working during the summer. (For the experience if he's one of the very few who doesn't need the money for expenses). He shouldn't be laying around any house all summer. 

If he comes, even if it's only for a week, I wouldn't go out of my way to entertain him. If he wants to tag along to whatever you usually do (library, play group, park)  fine. But, no outings just for him when DH is at work. No trying to be quiet, to keep your child quiet,  so he can sleep. Households with young children are not quiet in the morning.

I wouldn't want any of my SO's relatives with us for more than a week (and he would not even dare ask), so I think you have a point and your position is totally reasonable. 

It's one thing for him - it's HIS relative and he's not home all day.  I could see how this would be very uncomfortable for you.  If your husband can't see that, he's not very perceptive.  More likely he sees it and doesn't care, because he's more interested in accommodating his brother than in making you happy.  I also think your husband's way of dealing with this - shutting down because you didn't immediately agree to what he wanted - is very immature and not conducive to relationship success.  I think you are correct that this will not be good for your marriage.  I'd be surprised if you were not extremely resentful of your husband by the time his brother left if he stays the whole summer.  It's your home too, and you should have a say.  I never think it's good for another adult to be living with a couple for any length of time, and it's an especially bad idea if both are not totally on board.

No

What on earth is your husband thinking?

"Hey, hon, won't it be fun for you to have my adolescent brother here ALL SUMMER, while I work, and you are home dealing with him AND the kids? Good times, right?"

Even two weeks is too long. One week is fine IF your DH takes the time off to spend with him.

Did you speak to your DH at the time?  If not, you need to now, and tell him that you resent being turned into the maid for his family.  Is he prepared to tell his his brother he has to get a job, keep normal hours, clean up after himself and do chores?  I suspsect the brother thinks this is stay in bed all day, etc. 

Is that the way he always resolved problems?  By pouting and shuttting you out when he did not get his way?  Or is this something new?  I would address that pronto.  You don't want that to become a trend in the marriage!

If you are up for compromising at all... I would go back to him to talk further about this.  It sounds like when you told him "I don't want him here any longer than 2 weeks".. all he heard was "I don't like your brother"

So.. you go back to him and start off like this.

"Honey,  Can we talk? You know I like your brother Bob..we did have fun that time we went hiking.. he's a nice kid.  But when you told me the plan for him to spend the summer here, I got a little worried.  A whole summer is a long time to have a house guest.  With all the things I do with the kids.. and the house,  I really don't see having enough time to also play host and entertain your brother while you are working.  Maybe you could help me understand more about how this situation might work.  Ultimately, if he does come for the summer, we definitely need some ground rules so that we all can live happily in the same space.

1.  Car?  does the brother have one?  if not.. how will he get around?

2.  JOB.. he must have one.. or if he is independently wealthy.. he must have a full time volunteer position.. at least 40 hours a week responsibility. (possibly a little flexible if brother takes a class or two at local com coll.)

3.  Space.. he can only stay if you already have a room that can be fully dedicated to him.. the kids and all will not be uprooted for a whole summer.

4.  House Rules.. like a curfew.. and other rules about keeping house clean.. chores etc... Also rules as to NO houseguests.

5.  If Brother wants to see parents.. he can go see them for a long weekend.. not have them come here..lol.

5.  Financial contribution - He will pay a fair share of utilities and groceries and pay his way for all entertainment.

My husband approached me about letting his sister and her husband/two kids stay with us a few months ago. I didn't want to be the bad guy who says no to family, but I knew it would be a bad idea. They stayed for 3 months and holy hell, it was miserable. My husband ended up kicking them out after asking them multiple times to clean up after themselves and teach their kids manners. It was bad. Like, real bad. Like, the smell hasn't left my basement where they stayed bad lol. 

hubby arranged a family gathering at our home his sister catered for. Day before hubby tells me bil and wife and 4 adult boys are sleeping over. I sarcastically said oh and you’re prepping breakfast for them and hubby said i could... oh no no no i said, see mornings i’m busy pumping and breastfeeding my son so you’re delusional if you think i’ll prioritise cooking and entertaining family over breastfeeding my son in peace. They left by 8am the following morning thank god.

honestly i’m cool if inlaws stay over especially if coming interstate for family weddings as sil always helps out cleaning and laundry or cooking etc but some sit there on their butt while i’m heavily pregnant and expect i cook and serve them.. 

don’t feel bad standing up for yourself, you are a married couple and your husband has a duty to protect your privacy... did your husband invite his brother over or was it bil who self invited himself and hubby complied?

Is he wanting to have his brother there for support given the marital troubles you are experiencing? I might ask him that directly, because if that's the case, your DH needs to stop that and look for a counselor instead. As you said, having your brother in law around will hinder your ability to work through issues with DH - not only will you have another adult that you have to tip toe around if you and DH disagree, but the brother in law will be prone to siding with DH.