Uncomfortable conversation (am I wrong)

Hi everyone I really need opinions, I plan on having a conversation with my bf (uncomfortable one) backstory, he’s 30 I’m 29 we have a 7 years old son, broke up & reconnected and now we are pregnant with our second child. I moved in 3 years ago we live with his inlaws. In this 3 bd apartment there’s about 11 of us under this roof. Luckily my bf has his own bd (it’s the smallest one in the house. We struggled just us 3 so now unexpectedly pregnant I’ve been stressed how are we going to add another body in this room.

Our sleeping arrangement he has a full size getting a bigger bed would leave us with much smaller space than we already have. So my son and I sleep on the bed and he sleeps on the floor.

My uncle recently told me he will let us stay in his 3 bd house, my uncle only asked for 500 rent.

No one stays there he just asked us to take care of his pets while he stays with his dad (he’s taking care of him). For a year. I brought this up jokingly to my partner and he laughed it off now that it’s getting closer to our due date I’m truly considering this offer.

My bf pays 300 here in rent.

So I wouldn’t change how much he pays I would just add the rest. Am I wrong to ask of this from him?

He’s told me before he doesn’t mind how “tight” it is here he loves staying with his family, where I want us to start our own chapter already. Also, how would I bring this up?