They would most likely be young, like 15 years old and not related to each other. They may come from orbital space colonies, because they would be used to that lifestyle. Orbital space colonies would help us learn how to keep people alive in space so they would probably predate a generational ship by 30 years. Frozen eggs and sperm from 1000 people would help us maintain genetic diversity. Robots could be sent ahead to build an orbital space colony from asteroid material.