I'm so sorry to hear the news. I also have a family history of PCa and hate it!! The good news is that you are educated on the condition and will be such an asset to your brother and family during this time. You already directed him to an incredible resource here at HW.
I believe the odds are that if you have two family members that have Pca then your odds of getting it double and if there are three members in the family, then you are almost guaranteed to get it.
I need to double check, but I remember reading that somewhere. It's depressing, but we both know this disease is VERY curable if caught early and hopefully this will benefit both our families! Hang in there and let us know how we can help! We are a team.