My partner worries about this a lot as he has a very strong family history of aggressive prostate cancer - grandfather, father and uncle. His father has also had bowel cancer, diagnosed at stage 4 and was inoperable. Thankfully the tumour responded to treatment and he is in remission.
My dad is one of 5, his brother got blood cancer in his early 30s, he's been in remission since 2006, none of the others have had cancer. His mum smoked 60+ a day for 60 years and never got lung cancer although died from pancreatic cancer at 86.
My immediate family is much more prone to clots - my mum had a major stroke in her early 20s, my dad a mild stroke in his early 50s and my sister had a heart attack in her early 40s.
My partner does worry about cancer and I worry about strokes and heart attacks but we live for today, plan for the future in every way - looking at making prudent decisions now that will allow us to enjoy life and not be trapped in a work to survive cycle, not being so focused on planning for tomorrow that we don't sacrifice life today. We live healthily and are mindful of what we exposes our bodies too - mostly whole foods, no smoking, limited drinking, occasional ultra processed foods and so on.
The thing with cancer is not all tumours are equal. I do believe the 1 in 2 get cancer but that's not the same as 1 in 2 will die from cancer. There is a difference between someone getting a fast growing tumour in your 30s and 40s and someone getting a slow growing tumour in their 70s and 80s which may never become obvious. There are cancers which require no treatment at all, watch and wait and most probably something else will get you before the cancer does - this is particularly the case for some types of prostate cancer. It's not uncommon for autopsies on older people to show undiagnosed tumours that hasn't been impacting a person's life.
Its complicated and difficult for the brain to rationalise at times of stress. I would say for both myself and my partner we worry more about our family histories when there are other worries in our lives and for us it's a bit of barometer for our emotional health