As much as you want a father want his children to love each other, he can’t mandate it. Their feelings are their business — the only thing you can try to exert some control over is their behavior.
As a father, you can start by making it clear to them that no matter how they feel about each other, they must tolerate and treat each other decently. Bullying, cruel teasing, and tattling are not allowed — no matter who started it or what the other child was doing.
Don’t just forbid the negative behaviors, though. Offer them some positive alternatives: ways to solve problems. If they both want the same toy, don’t tell them what to do — ask them. Eventually they’ll hopefully come up with the idea of taking turns.
Though they’re very close in age, try not to force your kids into each other’s company. If you let them pursue their own interests, and allow them to have separate friends at home and school, they may well grow into a mutual solidarity that will amaze you.
Above all, respect each child’s dignity. Loving each as an individual means that you should never make either one look or feel small — to himself, to his sibling, or to outsiders. And, of course, never, ever compare them, much less hold one up as an example to the other. You may wish that this orange were sweeter, but you’d never wish it were more like an apple, would you?