Is the pronoun in this sentence an object pronoun..... Conran and his sister will sing a duet at concert?

The pronoun in the sentence is "his" and it is not an object pronoun.

Here's why:

* Object pronouns are used as the object of a verb or preposition. Examples are "me," "him," "her," "us," "them."

* "His" is a possessive pronoun. It shows possession ("his sister").

Let me know if you have any other sentences you'd like to analyze!