The hormonal phase sucks and is very painful. Mine turned from a sweet cotton fluff into a razor beak trying to draw blood at every given opportunity. That phase will eventually subside. They might get along great but you should get yourself a small cheap cage incase you need to separate them.Here is the thing in your situation. As said parrotlets can be aggressive and terrirorial. Your guys are very young. At the age they are now they are not a "bonded pair" they are effectively "flock mates". Good friends may be a better way of saying it. Within the next two years they will mature and go through a lot of hormonal phases, about the same as humans do from age 0-20. Some of those phases can be very volatile, mercurial in nature. So it is best to be prepared to separate them if one becomes over dominant and starts to bully the other bird. There is a joke / saying among bird people that it is all fun and games until somebody loses a toe. Sort of sums things up nicely in a dark undertone. So be watchful. If they get aggressive they will go for feet and eyes. Soon as they do separate them in cages where they can not get to each other in any way. Then wait it out for a bit. Parrotlets are sentient beings. Constantly changing, everyone its own special being. Most are very friendly loving critters. But they do have moods, and sometimes some birds are just more moody than others. So you will just have to see what your guys grow up to be. Things I do know that help in multibird situations. One is space. Big cages, both separate or together. Also I think free flight helps. The more room to run the less chance of a fight. With that still look for birds running from the other or birds chasing the other. Too much of that is a signal. Also, birds are like small children. Second thing is they get jealous easily and share it just as easily. Be that about food, treats or time with people. So just keep an eye one that and play it as it comes.
Now with that all out there I can honestly say having two birds is nice. I have done it twice for about a year each time and it worked well. But it does depend on everybody involved, bird and human.