Another tricky factor which you didnt mention was are they still in contact/living with your birth father?
Personally I dont want anything to do with my father so if my half-sister was still in regular contact with him, I wouldnt have anything to do with her because I wouldnt want my info filtering to him. So... if they are still in contact with your dad, would you feel comfortable with your half siblings sharing stuff about you with your dad??
Yes, see this is the most awkward thing. They still live at home with their dad and I don't have a relationship with him at all. I wanted to meet him when I was young and did so once, then I had to contact him back in '06 to get family history information for a uni assignment (genogram) and he basically told me on the phone then that he has his family and I'm a part of a different family and let's just leave it that way and go our separate ways...so I shook off the flip off and moved on with my life, not really reserving any thoughts of him, hence the major shock to be contacted!!
I'm currently chatting to my half-brother on facebook now, he's hilarious! He told me that he just found out last night and his words were, "and I'm totally tripping out!!" then said he noticed I have a couple kids and responded with, "hey, I'm an uncle! That's cool because I have a couple friends at school who are uncles too". lol cute!
They seem pretty eager to get to know me, which is nice, but at the same time, I feel some hesitation because of their (our) dad...I'm not sure how intentionally or unintentionally this has all come about so am a little wary!
I don't have to worry about meeting them anytime in the really near future as they live in NZ and I'm in Aussie (faar side). Although my half-bro is already suggesting that he wants to come to Aussie because he's never been before!