I have written about this sometimes ago and it is the same thing as yours. It is normal to feel surprised and the odd one among the others when you found out you were adopted but it wouldn't make any fuss when these parents treated you as one and equal to others without maltreating you whatsoever.
The only thing is to find out the reasons why my biological parents left me for another family, and if they are dead, all good and well. Life moves on.
That's just it, inasmuch as I've been treated equally between those I know as my siblings, then there's no point acting up.
It's just to be grateful and love forward to better days with them despite the revelation.