In my case, I trust my parents, so it's not an issue for me to share personal details about my finances with them, just like they share everything with me. But that is my case, therefore I can't say every parents are going to be trustworthy and loyal to their children, because there are situations where parents took advantage of their children and even commited crimes against them, while the opposite has also happened in other situations.
Cases of parents taking advantage of their children or vice versa are rare and we should be flexible if we are unfortunate enough to find ourselves in such a situation. Also, most parents are the most trustworthy people in this world because without them there would be no us, without their upbringing we would not be here today. So if we doubt our parents, then no one in this world will trust us, let alone give us the right to doubt others.
To tell people to not trust anyone is too extreme. I think you have to discern who you can trust from who you can't. At some point in your life, inevitably you have to trust someone, otherwise you are going to have a hard time doing business, making friendships and building a professional career.
I think people are just talking about outsiders, strangers because in life, we cannot survive without trusting anyone or without anyone trusting us. Everyone has closest relatives, people who accompany us in life. People who have no relatives, no trustworthy people are just failures because they trust no one and no one trusts them.
I would avoid talking to women about personal finances, though. If you don't avoid, it's going to be pretty hard to conclude if she is interested in you or in your money.
What about your wife?