Roots and the private self
This is the house of roots: your family, the place you grew up, your sense of belonging and the private person you are at home. It’s one of the four strongest houses in the system the app uses, along with the 1st, 7th and 10th, so a planet here tends to matter a lot even though it may hardly show in public.
Someone with the Moon here may need their home to feel a certain way before they can relax at all. Someone with Uranus here may have moved a lot, and they may still feel most at home with one foot out the door.
What it means for two people
The 4th house is what comes up when you first see each other’s apartments, or meet each other’s parents. It’s why one of you thinks Christmas is obviously at your mother’s and the other has never considered that. You each brought a picture of what home is, usually without knowing it was only a picture.
A partner’s planet in your 4th house tends to make that person feel like family fairly quickly, for good or ill. Their Moon there may feel like a place to rest. Their Saturn there may make you tidy up before they come over, even after several years.
Before moving in
It helps to ask what home needs to have in order to feel like home. Quiet? Friends dropping by? A full fridge, or a clean counter? You don’t need matching answers. You do need to know them before the lease is signed.
Family patterns come up here as well, sometimes painful ones. A chart can suggest where to look, and it’s a poor substitute for someone qualified if the past is weighing heavily on you.