<P> Aaron is one of the rescued Oceanic Six , and the general public are told he is Kate 's son , while Claire is listed as among the passengers who did not survive the plane crash . At Christian Shephard 's memorial service , Carole Littleton , who has recovered from her coma , tells Jack she and Christian had a relationship which produced Claire , revealing her to be Jack 's half - sister . Eventually , before departing to return to the island , Kate reveals to Carole that Aaron is Claire 's son . Kate tells Carole that she is going back to try to find Claire , and leaves Aaron with his grandmother . </P>
<P> Aaron is one of the rescued Oceanic Six , and the general public are told he is Kate 's son , while Claire is listed as among the passengers who did not survive the plane crash . At Christian Shephard 's memorial service , Carole Littleton , who has recovered from her coma , tells Jack she and Christian had a relationship which produced Claire , revealing her to be Jack 's half - sister . Eventually , before departing to return to the island , Kate reveals to Carole that Aaron is Claire 's son . Kate tells Carole that she is going back to try to find Claire , and leaves Aaron with his grandmother . </P>
when do we find out claire is jack 's sister
when do we find out claire is jack 's sister
At Christian Shephard 's memorial service
At Christian Shephard 's memorial service