Our boys are 16 months apart, as we 'planned'. There was a sweet spot between the newborn stage and teething where Jason was sleeping really, really well, and we thought, why not?! We knew we wanted more than one kid, and we figured it would be easier to have them in quick succession. After all, once diapering and night wakings and round the clock feeding and spoon feeding and all the other early life stuff is out of the way, would we really have the guts to start all over again? For many people, I have learned, it is far easier to start it all again, after a bit of break, than to double down and pile everything-times-two into two years or less. However, there is only so much you can tell new parents, and we had to learn on our own.
With a 16 month age difference, we knew it would be difficult at first. Our hope, though, was that as the kids got older, they would have more in common and be better able to play together by being close in age. Right now, we have two boys, a 3 year old and a 2 year old. When everyone is in a nice mood, rested and fed, the boys can play together without adult intervention for 20 minutes or more. This is how I have defined the reward stage of closely spaced siblings. It began shortly before Jackson's 2nd birthday, and as time passes, there is less yelling and arguing every month.
We work hard to engender cooperation and communication, with a lot of help from what we learned reading Siblings Without Rivalry. We talk a lot about 'taking turns' as well as about how 'hitting hurts' and 'kicking hurts'. When someone hurts someone else, we have to point out, "Look at his face. Do you see how upset he is? Do you hear him crying? When you [hurt/push/yell at/etc] your brother, it makes him very sad/hurt/angry!" Neither of the boys are at a point where they can emotionally manage stressful interaction. It takes a lot of work to teach the boys to pay attention to each other, to listen and be respectful. This has to happen with siblings of every age, but my boys are doing it together, and I like to think that for once, we don't have to put in twice the effort.
It certainly wasn't easy for the first year, but it did get easier over time. The boys really are good friends, though they have such different personalities. We knew it would be hard work, and it was. We hoped it would be worth the effort, and it is.