You can also find a bunch of video interviews that my half sister did when she found out by searching his name.
There are about 20 of us in contact now through 23&Me and Ancestry DNA tests, and at least 5 more that want no contact whatsoever. We get a new one nearly every month, and more so after holidays or sales on DNA tests. Estimations go into the thousands.
Luckily(?) my (real, not bio) dad was dead before he found out, but my parents had no idea.
Finding out was a serious trip. There were A LOT of implications with it, especially with meeting my half siblings. If anyone wants more details, I'm happy to talk about it.
Q2: What physical & behavioral similarities do you observe between you and your half-siblings? Do you have any insight on the nature vs. nurture debate?
My siblings and I have speculated the hell out of his motivations, and I've personally come to the conclusion that he was in a position to industrialize his evolutionary impact and took advantage of it.
Most of life has an implicit "purpose" to reproduce, and he found an extremely efficient way of mechanizing that, without any of the downsides like actually raising the offspring.
It's odd and I'm getting personal here but I always knew I wanted kids since I can remember, and I knew that if I never found a partner to have children with, I'd want to donate sperm for the sheer biology of it. It's an odd thing to try to express, but I'd be surprised if most people don't have some level of that.
2. As far as physical characteristics, I actually look quite a bit like him in many ways (especially the younger photos before he was drinking himself to death). But certainly better :D You can reference my website in my bio and the link in my parent post if you want to see. Eyes, hair, skin color, facial features, relative height, etc.
Behavioral - I was diagnosed with bipolar 1 disorder when I was 20. We could never figure out where that came from. It's treated now and also good to have someone to blame. I feel i share many personality traits that describe him, to certain (usually lesser) degrees.
They also say 80% of "intelligence" is inherited, and not to rag on my wonderful parents or prop myself up or anything, but we all sort of always wondered where I got that too vs my parents or other relatives. Also the aforementioned biological urge is a pretty interesting point - all of my siblings so far either have children or want them.
Most of my siblings are musical and play at least one musical instrument or sing or act or perform in some way, and he was apparently a great multi instrumentalist. The list goes on and on.
I'd put quite a lot more weight into nature than I ever would have before. I was convinced of nurture being the obvious bigger influencer but much of that could be attributed to lack of similarities with my family growing up. When I found out about this, I discussed it heavily with my siblings and some of their families and we all agreed that nature plays an enormous role that we'd never know otherwise.
How has the knowledge affected your life?
My feelings toward him are very complicated. At surface level he's an evil asshole who violated my mother and family and hundreds of others, not to mention things like his neighborhood reputation or highly debated "kidnapping" conviction (very long story, she maybe was one of those "kidnapped herself" stories, but it's debated).
But deeper down, I wouldn't exist without him, in the sense of "I" as my identity and ego and DNA which, frankly, I wouldn't have any different. I'm happy with how my life has turned out and how I've grown to understand myself and the world and having this knowledge has only built upon that. My mother has forgiven him and like other commenters has loved me anyway this whole time thinking I was her husband's, but it doesn't change her view of me or him.
At another, weirder, impersonal level, I have somewhat of a sense of respect and awe in him for accomplishing a biological feat only possible in a short window of time and space that he figured out and exploited. It's weird to reflect on it from a purely objective biological big picture perspective.
For example, every single new sibling talks about a lawsuit right off the bat. We have to explain to them each time that: The clinic went under, Lippert (the IVF technician/bio father) died in 1999, and the doctor overseeing it killed himself and destroyed the records. There is no lawsuit possible because there's nobody to sue, but also we'd have to prove some sort of damages, and being alive doesn't really count, for most of us anyway :D.
Most of us who knew early on are also a bit weary of discussing it with new siblings in general, and many of us have wildly different ideologies like politics and religion, so conversation gets weird fast at any gathering or chat group. Also some get really reactive and get really weird with us when we reach out before they usually completely shut us out. Some have been more intense in that regard.
2. GSA. https://en.wikipedia.org/wiki/Genetic_sexual_attraction. It's super real and has affected more than one sibling. This can be very intense, and intense attractions can lead to intense reactions. I don't know how much more there is to say about this other than reading up on it, but there are lots of examples of this and it's quite common in these scenarios.
Obviously this can lead to things like accidental (or purposeful) relationships (which is it's entirely own topic of discussion, esp with regards to marriage etc), or genetic birth defects of their kids. There aren't any examples of extremes of these in my situation that I'm aware of so I don't have any crazy stories, but you can see where it could lead.
Those are the big ones.
It can be quite pleasant too, and some of us have become close friends, I shouldn't leave that part out.