Dramatic reveal

As the title says. I'm here to ask about dramatic reveals and also small betrayel.

So I already have a somewhat complete idea about the scene. The problem is that I don't know how to do it and I really want the reader to feel it as well.

The concept is this :

Character A is been taking care of Character B since they were a baby. Character B is from a royal family which was slaughtered and one of the followers of Character B's father took Character B and took them to Character A. They asked Character A to take care of Character B and never reveal their past who their parents were or their homeland.

Years later Character B found out that Character A knew all along who they were and their origin. This causes them to argue with each other.

So my question is.

How is the a good way to reveal something like this? Through someone giving them a photo of them being a baby and in the hands of Character A and next to them standing someone else who they know?

Someone asked Character B if they ever thought about why Character A is so secretive and why they always change topics when Character B asks about their past?

Or some other way?

(This question is probably weird I know but I lack experience in making dramatic scenes when writing and I need guidance)