out that my uncle was actually biologically my father — and that it was not the man who raised me — I don't know that it would really change much of anything for me. I think, to me, because my uncle and dad shared a lot of genetic material I would see that as a natural limit on the variability this new revelation would introduce into what is already a pretty mixed up bag of how I came to be me (meaning that who I am is an ambiguous concoction of my genetic traits and my developed/learned behavior).

If I were you in this scenario (as opposed to being one of your cousin/half-siblings), I might wonder how my dad had always felt about my cousins, who he knew were actually his biological children. I don't think it would make me less confident in how he felt about me — but I don't know.