This structure is a tree: every summit except the root (Mount Everest) has exactly one parent.
Other peaks without parents are an artifact of an incomplete database, but otherwise it should be true.
Mount Everest
(8848.86 m) ↘
8848.9 m
(island high point)
Aconcagua
(6960.8 m) ↘
6960.8 m
(island high point)