Shannon is Boone's stepsister by marriage - but their relationship is a lot more complicated than that...
Early into the survivors' ordeal she establishes her poor little rich girl credentials - while the others ransack the fuselage for items of value, she rescues her bikini and indulges in a spot of sunbathing.
Her selfishness alienates many of the castaways, but it would be a grave mistake to underestimate her, as Boone has found out all too often in the past.
Manipulative and highly intelligent, there's definitely more to this anything-but-dumb blonde than meets the eye...