What are the root causes of Sibling Rivalry?

I have two older brothers and one older sister whom do not get along, although when younger they did so.
One Guardianship batlle that lasted 12 years over my late mother whom passed away at age 92 yrs old (2010) caused them to turn the family into a war zone.
Hardly anyone talkes with each other now, and the family had split into factions.
I do not think that they will come together at all. Both brothers are well into there 70yrs of age and the older sister is reaching 70 yrs old soon.
It is all too bad, when one would think that by the time they reached their senior years that understanding would develop?
Still waiting, but not holding my breath on this one.

Check out this fascinating news piece that ran on NPR today about new research that indicates that younger sibs are more affected throughout their lives by older sibs than even their parents. Very interesting.

@pachyderm I thank my lucky stars that I did not follow my sisters behavior.
On the service she appeared a nice person, while really ( at home) she was a mean spirited person.
( almost like a salesperson trying to sell something?)

A perception that their is not enough attention from parents to go around.

@talljasperman
Does this perception ever change when they mature?
Or is it carried into other relationships?(Spouse /coworkers /friends)
I think If these base issues are not resolved within that person, than it would
continue to be played out with people somewhat “like” the parents personality
that they have a problem with.
Failing to accept there underlying problem brings more problems with other people,
until they can resolve it within themselves
They have to realise that their self worth,had nothing to do with others.

@Inspired_2write Everyone needs to have someone that they can trust and share with… parents are the first place to look. Second are family and friends and spouse… Some holes get filled by teachers or role models…

@talljasperman
Does this mean that one is spending a lifetime trying to attain the attention
from their parents “still”?
And “when” does this need stop, if at all?

@Inspired_2write Like in the jungle, one does not let go of the vine when swinging until another vine is available. One does not let their parents approval go until they have approval from somewhere else ( hopefully oneself ). Either from a spouse or some other means, like addiction or approval from undesirable means. Later in life people may just choose to walk, or to have a go at life alone.

One does not let their parents approval go until they have approval from somewhere else
( hopefully oneself ).
Or Confidence?

@Inspired_2write The more secure one is the less they need to depend on others. That number of people that one needs to depend should never reach zero. Sibling’s competing over parents are going for the low hanging fruit… seeing it is easier to relate with someone that they had know all ones life. For example I’ve known my mom for 35 years and she more or less understands me better than a stranger. Humans are social animals and we always need each other for a shared meaning in life.

@talljasperman
Your mother sounds like a nice person to have around, to share in a meaningful life.