I've been adopted at early age and have no recollection of my biological parents. My adoptive parents have told me at a young age that I was adopted. Because this fact became integrated into my life so early on, it was a very normal subject for me to talk about openly.
Even so, I've never had much interest in finding out more about my biological family until recently. Because I am considering migrating to the other side of the world, I've felt the need to get touch with my biological family now that it's still somewhat easier to do so.
My biological mother left me a letter stating that she doesn't want me to come looking for her. Given her reasons, I want to respect her request. However, I want to know if I have any siblings, because I was raised as an only child. So, I got in touch with my country's official institution for lineage questions.
They have been very professional about handling the situation. I have learned that I indeed have one half-sister, who is of legal adult age in my country. So, in my opinion, she has the right to know of my existence (if she doesn't already), even without my biological mother's consent. Also, I have the right (as per European Union laws, I was told) to know who my biological mother and half-sister are.
Now, a potential problem has presented itself. The institution, who mediates all communication, has informed my biological mother of my intentions. They did this to inform my mother of my intentions, and present her with the opportunity to tell my half-sister herself, if she hadn't done so already. While I expected that she did, it turns out she didn't. That means that my half-sister is soon to learn about something that has been kept hidden from her for her entire life, approximately 25 years.
The truth-bomb that is this revelation and the emotional impact that it can cause has made me doubt if I really should be doing this. The institution has re-assured me that I'm not at fault here, and I am still fully within my rights. Still, it makes me feel like a bad guy. At any rate, the information is going to come out soon, even if my mother decides not to tell my half-sister herself. The institution will contact my half-sister personally to further progress my case.
My goal with the institution is to make my half-sister aware of my existence, and let her know that I am open to contact if she wishes so. I'm leaving this in her hands, basically, but I feel at least she has the right to know.
Now, assuming she reaches out to the institution and agrees to a (neutral environment, institution-supervised) meeting, what are the pitfalls I should watch out for when engaging in conversation with my half-sister? I have absolutely no idea what it's like to have a sibling, let alone how to talk to one who only recently learned I exist.
I'm actually dreading a meeting, but at the same time hoping she agrees to one.