Answer: The character that is part of the Montague House is Balthasar.
Explanation: William Shakespeare's Romeo and Juliet (1595) focuses on the rivalry of two families: the Montagues and the Capulets. Romeo, one of the main characters of this tragedy together with Juliet, belongs to the Montague House. Balthasar is also part of this House since he is Romeo's serving man and his friend. Balthasar is the one who informs Romeo that Juliet is dead in Act V believing that she is actually dead.
