Interstellar colony ships can not transport humans who are not embryos. These colonists are born from artificial wombs within several first generations of the colony, but the very first generation must be somehow raised up and especially well trained. The alternative to bringing up by androids is using memory chips: while the future colonist grows in a tank, they see intricate recordings of all senses of their clone sibling brought up on the Earth. This technique raises lots of problems but its relative benefits forced to find plausible solutions. For example, gradual separation procedure takes a person from believing that the life in the chip is their own finally to consider the clone just their brother or sister.
Marine was one of the very few "Lilith" crew members who had a man to truly call "father". Finding her recordings centuries later was a great shock to the planet's society.