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If they are ... sigh, were ... both "baaaad" types, and Greg the one always winning, always with the cash handy, etc etc, the dynamic could have been extreme frustration for the "baaaad" brother always getting shown up.
Just surmising, but the Cain-and-Abel syndrome does not sound implausible to me.
Well put - hard to imagine how a parent makes it through such a chapter in her life.