I completely understand where you're coming from. My siberian huskies are littermates and they're now a year and a half old.
The day after I brought them home, I read all those same stories on the internet (probably the same sites you're reading) and I was horrified They basically said how raising 2 pups at the same time was the worst thing I could ever do and I should get rid of one ASAP.
Well, they were dead wrong. My boys are best friends, completely inseparable. Even now, at 18 months old, they still like to cuddle up to each other when they sleep - I hope they never grow out of that.
They're also very bonded to my husband and I, and we couldn't imagine our lives without them.
The thing to remember is, even though they have each other, it's still just as important to socialize them with other dogs. I also find that my boys play much more rough with each other, than they ever do with their other doggy friends - I think it's a sibling thing.
As for training, I found it was easiest to do it separately. My husband would take one outside and I'd work with one inside. Otherwise, I found it was too confusing for them when teaching commands like sit and down because evidentally, one would do, one wouldn't, but they still thought the praise was for them. It's also harder to teach them their names if they're always together.
That being said, it's always been a nice little break for me to let them go off and entertain each other for a while.
Just remember, at this age, they'r still learning from each other what's acceptable play and what's not. If one of them gets too rough, the other will give a little yelp to let her know. But if at any point they're getting too rough for your comfort, you can just grab them each by the scruff (gently, as their mother would have done) and separate them. Make them sit and wait until they calm down. They'll learn quicker than you think.
Good luck with your new little bundles!