Just do it. I was contacted by half siblings, 3 of them all born to different mums during my parents marriage, we also have a (birth)father who dabbled in crime. Here's out its panned out.
Sister 2 who instigated the search and found all of us really isn't on board due to the terrible problems it caused in her family, and the betrayal she felt towards the wonderful man who had brought her up. Sadly he died within months of her finding me and subsequently getting in touch with our birth father who I had chosen to not have anything to do with decades earlier. He was however always on the periphery of my life like a ghost. As for my sister, we really are just facebook friends, we have a family page, and that's about it really. That's said though, she really was not in the right place emotionally to begin with, her granny had made a death bed confession about who her father was and that started off a search that she really wasn't ready for in real terms.
Sister 1 - we have had many happy hours together but after a while it became complicated. I realised she's an alcoholic and I cant cope with her. Sadly the situation that unfolded after she had been found made her alcoholism worse. I also have a situation in my life that means I have enough to think about around the clock and I just couldn't take her alcoholism on. I spoke with the family section of AA and did try to live with it albeit from a great distance for a couple of years but eventually I just had to protect me and mine and leave things be.
My brother - I have a brother. A brother, a fab wee brother, a real brother. We are family in every sense of the word. We lives thousands of miles from each other but we manage to get together every few months. My husband is a brick and makes it possible. We are both very sad the way things turned out with the girls and part of sister 2's problem is that her mum and my brothers mum were pregnant at the same time - there's 3 months between them. It was a great shock to my sister to realize she wasn't the result of some great love story but in her words - something sordid and dysfunctional.
My mum is long dead, and my beloved (step) dad is the only man I will ever want as my dad, my mum wouldn't have minded me being with my siblings because she was that type of woman - lovely, and my (step) dad has supported me through the minefield that unfolded at times. He just used to say I don't want you getting hurt. He likes my new family and is happy I have someone else to love me - my brother. I had been quite on my own in the world apart from my husband and children till my brother came along and it worked out the way it has.
As for my sisters, of course we are sad the way things have turned out but we know we did all we can to keep things going, and my brother is still in phone contact with sister 1. He also has a brother with a drink problem so kind of had a head start on me with how to deal with it. I jut cant.
My sister from my mum and birth dad has a troubled life and has not had anything to do with the new siblings. And my other half brother and sister from my birth dad and step mum will not have anything to do with them either because they don't want to upset their mum.
My birth father has made contact with one of his children, sister 2 who started the search. Our birth father made a trip to our home country to see her. He also saw my brother on his next trip about a year later, for an hour, and my brother has no need to see him or have contact with him again which is a good job really because I doubt any would be forthcoming - my step mum has not really coped with the whole things which is strange considering she thought it was ok when it was just a rumour the children existed and it had been my mum it had happened to. But of course now its in her back yard so to speak - mmmhhmmmm
And just to clarify - our birth father lives many time zones away from where it all started, and I live between both places.
So that's it really. Im glad we all know of each other and the lovely children and grandchildren from each other but at the same time there is an amount of sadness due to how things have worked out with our sisters. If you can cope with whatever may unfold if you contact your brother then go ahead - but if not then I would say don't do it.
hth :)