Relative pronouns serve a double use. They act as subjects or objects inside relative clauses. They also connect relative clauses to nouns or pronouns in other clauses, rather like conjunctions. Relative pronouns used as subjects or objects replace words like she or him. Note that one subject or object in a relative clause is enough.

Compare:

She has a son. He studies abroad.
She has a son who studies abroad. (NOT She has a son who he studies abroad.)

This is Mr James. He works with my brother.
This is Mr James who works with my brother. (NOT This is Mr James who he works with my brother.)

I couldn’t find the keys. You were looking for them.
I couldn’t find the keys which you were looking for. (NOT I couldn’t find the keys which you were looking for them.)

Whose

Whose is a possessive relative pronoun. It replaces pronouns like his/her/its.

He has a girlfriend. Her hair comes down to her waist.
He has a girlfriend whose hair comes down to her waist.

Position of relative pronouns

Relative pronouns usually follow their nouns directly.

The idea didn’t excite me. She put forward the idea.
The idea which she put forward didn’t excite me.

Here the relative pronoun which comes immediately after its noun the idea.