Hi Dalailama, I can certainly understand why you are feeling frustrated living with someone with OCD. It is a very frustrating form of anxiety disorder and in my experience also extremely difficult to treat . The first issue is that the person involved must acknowledge that the thoughts they have around their obsessions are indeed anxiety based and not "real" or healthy. They must then have the desire to want to challenge the thoughts which for them is usually pretty scary as often the obsessive thoughts come with a kind of threatening aspect to them , like " if you don't do this , something bad will happen".
The thoughts have usually made the person believe that if they do some sort of ritual , they will be spared the consequences of the bad outcome. So ... For example , someone with OCD might believe that you need turn a light on and off 3 times instead of just once or else one of the kids will be harmed.
Now many people live with their "secret " OCD thoughts and rituals and never present for treatment. But if it is interfering with their life , upsetting them, or the lives of people around them, then I think it's time to get some help.
The first point of call is your GP.
There is info on the Beyond Blue website ,and also the SANE website has info about dealing with someone in your family with OCD.