My half sister didnt know her step father wasnt her real father. She found out when she was 19 because another half sister of ours (my father got around) found her on Facebook.

It shattered her.

I was told when I was 5 years old by my mom I was adopted by my step father. She did it in a shitty way, (during their messy kids in the middle divorce) but at least she was honest.

Definitely prefer the way I found out, to the way my sister did. Finding out young, I think it was easier for me to adapt, and have support. My sister still doesn't have a great relationship with her mom and step father, and it's been some years.

Kids don't like it when their parents lie to them, who knew.