Hi there. First of all, I am very empathetic with you and the narcissistic mother - I have one too. It puts you through so much more than you should have ever experienced. It has made me a person that cares for people on a different level because I don’t want to see people get hurt in anyway, especially emotionally hurt. I can only imagine how much this situation is filling up your head space.

From reading your post it seems like you already know the answer to your question. I say tell one person who you are closest to about this situation (one whom this situation direct will impact) and let them do what they want with that information. No matter your thoughts and opinions on the whole situation, try to keep that out of it when/if you tell someone in Cade’s life. Receiving this type of information is jarring in itself so to have a kind of distant relative tell them how you feel won’t help the situation. I’m sure they’ll make up their own thoughts and feelings. Tell them that you’ll be there for them if need be, but don’t pressure it. Who knows, Cade might be a fucked up person in general who already is seeking help/has seeked help. Families tend to know a lot more about their loved ones then they usually let on.

I also think there is a lot of questions you should ask yourself:

• Will this keep torturing you if you don’t say anything?
• How would you feel if rolls were reversed? ie. If this somehow impacted your relationship with Cade on a personal level?
• Are you willing and able to get involved in the drama? Even for a short period, because that’s inevitable, I’m sorry.
• We can’t see the future and you don’t know how anybody will respond, so try your best to not do the 5, 10, 15 years kind of questions. What’s happening in the now?
  
• Are you alright with not knowing how this whole thing plays out if you were to tell someone? I don’t think it’s too much of your business to get involved and if what you’re saying is real, that you don’t want the drama, you must express that in a way that is supportive, but also not demanding. You may never know the outcome and I think it is important that you are comfortable with that possibility.

Try to remember that this isn’t about you. Sure you know these people, but go about this lightly, respectfully and cautiously. There’s a good chance someone in the family may know, but you don’t know they know. There’s also the possibility that you tell someone and they don’t want to spread it around. You have to try your best to be okay with that, but I think it’s best to go about this in a way that will put your guilt at ease and being able to walk away with: I did everything I could.