Maybe mold, bad water, bad pipes, some other toxin like radon??

Old house, new house?
city water, well water?
was the place built on a old dumping ground or low land that was filled?
Or high power lines nearby?

If a family in a home is having health issues , I'd check the inside & local environment for any type of cause.

If renting ask landlord about testing, or city/county health department, if landlord doesn't follow up..
How long have you lived in the place you are at?