Some companies treat family history differently so if by any chance you are loaded for one or other of them shop around, try a broker who might know different company policy. My mother died of cancer and one company I applied to put a loading on for me but another did not so went with them obviously. There is no indication that there was/is a hereditery element to the particular cancer so different underwriting policy in companies. All my father's family have heart issues but not at an early age so no loading there either in my case.
Fill out everything, even any random doctors visit if asked, first thing they are likely to do is send out a report to the doctor for completion, pretty standard stuff, then depending on that maybe a medical but not very common. The ages family members got certain illlness matters as well, younger worse than older obviously.