People who belong to the same family by birth "are related to" each other:
I grew up calling him "grandpa", but we're not technically related to each other.
You can say that people are "related to" each other, or you can just say that they are "related". But you can't just say that one person is related:
A: Johanna is related.
B: Huh? What do you mean? Related to who?
A: I mean, she's related to me.