Does the susceptibility of prostate cancer to radiation run in families?

Yes: A man with a brother or father with prostate cancer has double te risk of developing prostate cancer than a man with a negative family history.

No: The ability of radiation to kill the cancer depends on the sensitivity of the cancer and influenced by the extent of cancer and if limited to the gland, and grade of cancer. This varies between individuals even in the same family and does not run in families.

Susceptibility: Puzzles me, do you mean doing well with XRT forecast that others in the family will do well, or the opposite, that the side effects in oone family member predict for everyone having bad outcomes. Frankly, i don;t think either is true. Choice of treatment for prostate cancer is rarely based on fact or data, but intuition and projecting from others experiences plays a huge role.