This is my nephew's garden. – It's garden.

The Labour Party's spokesman made an important speech today. – spokesman made an important speech today.

You and I are responsible for this. – It's responsibility.

There's someone's bag. – Someone has left bag behind.

She was given some beautiful earrings and was wearing them at the party. – She was wearing beautiful earrings at the party.

Those people are my girlfriend's parents. – They are parents.