informal if people breed like rabbits, they produce too many babies very quickly.
It's like I was saying to Derek, they all intermarry and they breed like rabbits.
breed like rabbits
slang To have several babies in a short period of time. (Rabbits are known to produce a large number of offspring very rapidly.) I can't believe my sister is pregnant for the fourth time in five years. She and her husband just breed like rabbits!