Hi Rich

Prostate cancer  is a significant risk as people get older

1 in 14 get it after the age of 60 but only 1 in 10,000 under 40 so if your father and his cousin were older then that's not a strong likelihood of a genetic link but if they were in their 40s that would be different and unusual and worth talking to your GP about

Certain things give you a higher risk see here:

prostatecanceruk.org/.../are-you-at-risk

Having it in the familly is one of those things but probably only something you need to worry about after the age of 50