How do I ask my parents if my SO can move in with us?

Tori
I am 20 years old and graduating college in May, along with my SO of 3 years. I will be moving back in with my parents temporarily until I find a stable job and save up a decent amount to get my own apartment with my SO. Up until a few months ago, the plan was that we would both live with our respective families until we saved up enough to move out together. Unfortunately, due to a long string of events that I don't want to get into, his family was evicted from their home, and forced to move into an incredibly small 3 bedroom apartment. With his parents and 3 (significantly younger) siblings, there is no room for him in the apartment. He does not even have a bed available for him to sleep in if he moved back in there. There is plenty of room at my house, and I want to ask my parents if he could move in with us. My SO is completely willing to pay rent and do chores, he has no intention of mooching off of my parents, however I am nervous about approaching the subject, and am worried that if it is approached wrong, they will not even consider it. Any advice from ladies that have done the same/ or have had adult children ask this type of question?