I want an advice: Could a romantic relationship in which a person knows completely the other, but the other does not, be an equal relationship?

Anyone who thinks they can completely know another person is incredibly naive.

Sounds practically unequal by definition, except for not having defined what you mean by “equal” or “fair”.

And as janbb just wrote, knowing someone completely seems like a delusion to me.

As for what if the other person has a hidden side… I think that everyone has some hidden aspects, and that to the degree a person withholds and doesn’t share themselves fully with someone they’re in a relationship with, then to that degree, the relationship is not fully with all of who that person really is.

And since many/most people have obstacles and defense mechanisms and lack of self-awareness and communication skills, people tend to not be able to fully share themselves even if they think they want to.

And, people also develop, and change over time, often as a result of their relationships. Yet there is a common cultural conversation that assumes and expects that love relationships should be about two people being perfect for each other and not changing…

@Zaku: I don’t think that the people in a relationship being “perfect” or “perfect for each other” is the same thing…

That sounds like a setup to a very manipulative and abusive relationship.