One adult child whose siblings allow, by deferment, silence, or proximity, to assume and shoulder the predominant responsibilities of caring for an aging parent.
A sibling sucker with no time to call their own, can grow to be an angry angel.
A sibling sucker is usually performing one of the most difficult and thankless jobs on the planet.
A sibling sucker spares brothers and/or sisters of their equal responsibility which might "God forbid" interrupt their busy lives.
A sibling suckercan be one whose halo has fallen a few inches to become a noose.