There are at least two townhouse which can get two beds without loosing anything, plus at least one manor would get the bedrooms wing
So that's a potential of at least 6 kids that can be adopted

In theory, if you equip all houses, the maximum would be sixteen (2 per house/manor)

My question is ... does Bethesda support that ?
Can you really addopt more than two ? And if so, what's the maximum ?

I know there are plenty to adopt, all the orphans in various cities, plus the honorhall orphanage
But can you adopt them all (provided you got the space) ?

Nope, sadly 2 is all you get. I wish we could adopt them all as i have plenty of room for them and plenty of people to watch them when im gone, but no, they restrict you to 2. Unless somethings changed recently i wasn't aware of.

2 only, sadly.

You live in one house, no matter how many houses you own, children can only stay in the family home.

Two per character/playthrough. So if you have multiple characters, you can adopt more than two children.

Sad, I was hoping to be like mother theresa, saving all the orphans of Skyrim.

It's a bit silly since so many live in the street. or worst, in the wilderness

I'll settle for Proudspire as a safe haven for 2 kids then.

I'd agree with this as long as you don't fast travel or make that a habit. Fast traveling has been known to exacerbate this event once you've hit the milestone which triggers the reappearance of dragons in the MQ. So fast traveling to Solitude often can cause you to frequently experience dragon attacks on that city hold. And that's on top any extra damage from the civil war, if you side with the Stormcloaks.

But other than that, I totally agree Solitude is the most secure city stronghold and home in the game to keep the kids. I particularly like it because of this beautifully enhanced version of the city:
http://steamcommunity.com/sharedfiles/filedetails/?id=84637410&searchtext=

Between this and the More Trees in Solitude mod, Birds of Skyrim/flocks of Skyrim, and the 101 Bugs of Skyrim mods, the city couldn't be more aesthetically pleasing playground for the kids. They also get to play with the other children and pets in Solitude as well

Wow, wish this was in the vanilla game! Beautiful!

Truth be told, I'm rather glad of this. The alternative strikes me as kind of like being the bigamist who has two seperate spouses and families, who are totally oblivious to one another.