Is it illegal to withhold personal information from your adopted child?

Unfortunately, no. Its one of the reasons closed records are so very, very wrong. I inherited the genetic "gifts" of cervical cancer and cardio myopthy from my first mother. Without Australia's open birth records and reunion with my first mother I would be dead by now......I had cervical cancer, but wasnt aware of it until I met my mum, I also have cardio myopathy.....my doctors had been scratching their heads for years trying to work out where my heart problem came from until I met my mum and we noticed that ALL the females in our family have very tell tale red palms on our hands......my first mum has now died of the condition........but my two half sisters and I are all being treated and for the first time in years my heart condition is stable.