fathers among you will eat their sons: This terrible event would happen during a time of severe famine (a time when there is no food). When people become desperate and have nothing to eat, such suffering can occur (see 2 Kings 6:26–30).
This was also one of the covenant curses (the promised punishments for disobedience). God had warned that this would happen if the people rejected him (see Leviticus 26:29).