I would never lie about somthing on a medical. You never know what could happen in Doha, if I was to be poorly because of somthing I hadnt mentioned in my medical my health insurance would become void. Never lie on medicals, although lieing about somthing a family member had or has is a bit different to somthing you have personally.
I'm over the experience now infact I'am actually relieved after reading these forums. I just take good things from the experience, for example I was able to get through the interview and pass, it was just the medical which let me down.
Good luck to the rest of you going to Qatar open days and going through the medical process xx