Prostate cancer doesn't run in families as such - but being a man makes it highly likely that you will get prostate cancer at some point if you live long enough. About 5% of prostate cancers are thought to be genetic - so not just whether your brother has it but if you have close female relatives who were diagnosed with breast cancer in their 30s or 40s, close male relatives who were diagnosed with PCa in their 40s or early 50s or breast cancer at any age, close female relatives who have had uterine or ovarian cancer, then it may be that there is a gene fault.
As you have realised, the DRE finding is indicative and you are preparing for the news that you have cancer although it is by no means certain. If the biopsy does confirm cancer, it will be important to meet an oncologist as well as an urologist in order to discuss your kidney issue - depending on where the cancer is and how much there is, it may be that brachytherapy or a more targeted focal treatment is possible.