They (referring to women or girls) are my best friends.

His success had a cause-and-effect relationship with his efforts.

He and I are related by blood.

There is a complex love triangle between them.

This is the book that I am reading.

His claim does not match the actual relationship.

The police only informed the authorized persons about the information related to the incident.

There are many interests involved in this project.

It's difficult to understand the context of this sentence.

That issue is irrelevant to our discussion.