On the bus last week, a woman asked how far apart in age my children are, and when I told her five years, she shook her head in dismay, then began moaning and muttering about how it was a problem, a big, big problem. Her own two children were twenty years apart, and they still struggle with sibling rivalry. No assurance on my part of the mutual adoration between my girls could calm her; she was clearly frazzled, thinking of all the difficulties we are sure to encounter in the years to come.
I know they will argue sometimes; they already do. But I think that mostly they will love one another, look out for one another, be there for one another. Because they already do that, too.