Sibling rivalry is as old as Cain and Abel, and is probably inevitable. Parents can do a lot to either minimize or maximize it, consciously or not. This rivalry is usually at it’s worst during the difficult early teens, when everyone is developing their own personality. As we mature, we often accept our differences and get closer.
In many families, the estrangement remains and even grows throughout life. This could have been prevented by the parents early on, but they were indifferent, or even encouraging it. Labeling children at an early age with hurtful adjectives, such as the black sheep in the family, the lazy one, whatever, could leave emotional scars that last a lifetime. The one receiving the negative labels will probably leave home before they are ready, or try anything outlandish just to get attention from an indifferent family, which is never forthcoming. They could spend their life distrusting anyone who accepts them as they are, or shows them affection.
As parents age and become more dependent, the realization that they should make peace before it’s too late becomes overpowering, and the estranged sibling may be haunted with thoughts of what could have been and might have been, and makes an effort to get close, or even move back to the same town he left behind. This effort may be greeted with a superficial closeness or mild indifference. At times it does make for a new beginning.
Having a close sibling relationship is a great thing to have as we get older. A port in the storm, where you can always find refuge. Many people waste a lot of their life obsessing over this, wasting precious time blaming themselves. Instead they should be enjoying whatever they have achieved. Maybe very late in life, the closeness they never had will happen, but if not, let it be.