Put simply, you and your family produce water vapor by, cooking, washing, breathing, drying clothes, having indoor plants, animals,, sweating, children.
All this water vapor is held in the air, while it is warm.
Once you turn the heating down, or the outside temperature drops below dew point, that water vapor in the air heads for the coldest surface to conttdense.
You can see the condensation on the windows, this is good because you can wipe it up and it does no harm.
Elsewhere, you will have absorbent cold surfaces that will soak up the water vapor unnoticed.
Solutions, keep the air temperature up and the water vapor won't fall out.
Buy and use a de humidifier, this will provide a colder surface and most water vapor will head for it.
Do not cover the windows when it gets cold. Usually during the day the warm air circulating in the room keeps the window surface warm and the water vapor condenses somewhere else.
Open the windows, usually the air outside is colder and drier and the water vapor will move outside.
Fit treble or quadruple glazed windows, this again will raise the window surface temperature and move the condensation elsewhere.
Fit and use a ventilation system with a built in heat exchanger.
Use a exhaust fan in the bathroom when washing and another when cooking in the kitchen.
Exhaust fans with heat exchangers are best, ones with air tight covers as well, are better