Hi Madamez,
I was given up for adoption at 9 days old and was always interested to know where I'd come from - not through any longing for a new family or anything I hasten to add.
I found my original birth certificate in a drawer at my parents and used the details to get hold of my adoption file (via an Adoption charity in Manchester). Once I'd got hold of the file I told my parents and they were supportive but a bit upset.
I didn't do anything with the information for a few years, till I was bored one day at work and decided to look up my birth mother's name on Friends Reunited - and while she wasn't there, there was a boy a year younger with the same surname. Knowing she had a brother, I emailed him asking whether he'd lived in the town she was from. He replied the next week saying yes, and did I know the family - so I told him who I was and apologies for imposing on him. I knew that he knew about me by the way, as it said he'd been looking after her when she was pregnant.
He passed my details onto her and she emailed me - for a few weeks we mailed and texted then it all got a bit intense as she wanted to meet up but I wasn't ready. That was 6 years ago and we still haven't met! In fact, I have barely communicated with her since then, but am in regular contact with 2 of my 3 half brothers who are a few years younger than me. I hear about her through them, so I assume they tell her about me (but maybe they don't) - I never told her I'd moved to the US, or had a baby, but the boys know.
Sorry for the long message - I think finding out about yourself is great, and even if you don't build a relationship with her, you may come out with some other friendships with random siblings!
Good luck