Please share your input on this, im freaking out a little bit?

I agree with the first two answers, he sounds like a great man. It is definitely not wrong at all for you to feel like he is your dad, because that's what he is to you. He's your dad. Maybe not biologically, but in all other aspects, he is, and a great one at that. Don't worry about getting a new sibling, I am sure that he will continue loving you guys as if you were his very own, because that's what he's been doing the whole time. He's a great man, and you should definitely keep on treating him like he's "dad", because he is.