Moulds can make people ill, particularly if they have breathing problems such as asthma.
Moulds can be treated with sprays for this purpose or if the surface is suitable a weak bleach solution; although this will take the colour out of some surfaces.
Moulds tend to flourish in areas of high humidty and poorly aired rooms. Opening windows and increasing air flow can help. Also try not to allow steam to condense on surfaces in the home, i.e. open windows when cooking, try to dry clothes outside.
Hope this helps.