Hi Doctor X
I'm married to a wonderful wife who has done nothing but embrace the fetish I have of dressing up as Batman and even going as far as getting a Catwoman costume and indulging in my fantasy with me. However, I've also realised that I have feelings of bisexuality and I would really love to explore them one day. Unfortunately, my wife is not willing to let me have that experience. She knows I love her and nothing will change that but it's frustrating not being able to explore this side of myself.
It is a wonderful feeling of having a partner that understands what we like and is accepting of it. For us that have particular fetishes it is scary to even mention it at times in fear of rejection, especially one involving superheroes and superheroines.
Sometimes we have other sides that we do not let out, in your case a bisexual curiosity. While we might see it as natural you have to understand the emotions of your wife. Yes she is accepting in your fetish and apparently shares it, she is uncomfortable to 'share' you. While it is easy for a person to say 'nothing will happen' and 'she knows I will always love her' to her it creates an opportunity for something else to change, namely each others feelings towards one another. In the end she wants a monogamous relationship. Also she might be a little insecure in how far things will go with your fetish.
Over time, she might welcome the experience of your bisexual curiosity but in order for you to have a healthy relationship with her, you will need to understand that that opportunity might never come. Good luck.