Let them know that this is a true story. Introduce vocabulary that you will be using that they may not know. Words like ancestors and siblings. Explain to students what family history is. Discuss that it includes things that have happened hundreds of years ago, and also things that may have happened last week.
Family history is something that is in each student's history.
Ask students questions about their own family history. Ask for some stories. Using the information from the discussion, have students prepare one question to ask the guest speaker. Review students questions before the guest speaker arrives. Stories would be very appropriate for this occasion.