Temperaments play a factor on whether children get along whether close in age or not. Spacing is more a question of what is more convenient for parents then siblings. Some parents think that having children close in age will automatically produce a friendlier atmosphere. Others think that putting a larger age gap between siblings encourage mentoring from the older child to the younger. However, these situations are only an ideal.
Children are volatile and nothing can guarantee a desired outcome.
Children close in age can rely on each other more than those that have a larger age gap. They become self-made playmates for each other. If children are the same gender they can, often times, be drawn to similar interests. They often learn from and begin to rely on each other. However, the drawback in having children close in age can be the tendency to group them together.