Hello G@chi, and a warm welcome which takes an enormous amount of courage to post a comment.
Feeling as though you aren't depressed or suffering from anxiety could mean you are in denial, although I'm not qualified to say but have been in exactly the same situation myself, andI'm also a twin, fraternal.
I have also felt the same as how you feel, not being recognised, although I've never ever had any problem with my twin anytime at all, so I'm very sorry this has happened.
Everybody can make a mistake, it's unavoidable, no one could ever be right in every decision they make, so we should be forgiven and given the opportunity for a second chance.
What we do and what we remember from growing up, can lay a base on how we are able to perform later on in life, then we can build on it, learn from it in a positive way or with a negative and/or detrimental attitude, but we can only believe how we feel at that present time, and if you need to talk to someone then your doctor or perhaps KidsHelpline 1800 55 1800 either by phone, webchat or online.
I can certainly feel for this situation you are in and hope to hear back from you.