Is it normal that when someone close to you experiences trauma in their marriage for it to bring up past trauma of things in your own marriage?

That's completely normal- your natural response to hearing about trauma is to relate with your own experiences. Even things that I've already mentally dealt with just bubble up to the surface anytime someone talks to me about issues they've had in relationships, especially when it comes to emotional abuse and blackmail. It's usually incredibly painful for me to relive those memories, but, the silver lining is that you know there is someone going through a similar trial in their life. Sometimes opening up about it to each other and sharing the things you've gone through can help clear the fog away and reveal the path your gut wants you to travel in.