Newtonsoft deserialization adds nulls to list
<p>I'm simply trying deserialize some JSON from a file into a list of objects, using the Newtonsoft JSON library in C#. Here are the contents of the <em>MeetingFile.txt</em> file:</p>

<pre><code>[
  {
    "People": [
      {
        "FirstName": "Malcolm",
        "LastName": "Reynolds"
      },
      {
        "FirstName": "Hoban",
        "LastName": "Washburne"
      }
    ],
    "PairDate": "1/14/2016"
  }
]
</code></pre>

<p>And here's the code for deserializing the object graph:</p>

<pre><code>using (var streamReader = new StreamReader(@"C:\Temp\MeetingFile.txt"))
{
    var fileContents = streamReader.ReadToEnd();
    var meetingHistory = JsonConvert.DeserializeObject&lt;List&lt;PairHistoryItem&gt;&gt;(fileContents);
    var serialized = JsonConvert.SerializeObject(meetingHistory);
    return meetingHistory;
}
</code></pre>

<p>And the classes:</p>

<pre><code>public class Person
{
    public readonly string FirstName;
    public readonly string LastName;
    public string FullName =&gt; $"{FirstName} {LastName}";

    public List&lt;IPairHistoryItem&gt; PairHistory;

    public Person(string firstName, string lastName)
    {
        FirstName = firstName;
        LastName = lastName;
    }
}

public class PairHistoryItem
{
    public List&lt;Person&gt; People { get; }
    public DateTime PairDate { get; }

    public PairHistoryItem(Person person1, Person person2, DateTime pairDate)
    {
        People = new List&lt;Person&gt; {person1, person2};
        PairDate = pairDate;
    }
}
</code></pre>

<p>But for whatever reason, this is what's contained in the <strong><em>serialized</em></strong> variable in my deserialization code:</p>

<pre><code>[
  {
    "People": [
      null,
      null,
      {
        "FirstName": "Malcolm",
        "LastName": "Reynolds",
        "PairHistory": null,
        "FullName": "Malcolm Reynolds"
      },
      {
        "FirstName": "Hoban",
        "LastName": "Washburne",
        "PairHistory": null,
        "FullName": "Hoban Washburne"
      }
    ],
    "PairDate": "2016-01-14T00:00:00"
  }
]
</code></pre>

<p>Where do the nulls at the beginning of the list come from? As far as I can tell, the JSON in my file is formatted properly. Am I missing some setting for the JSON Converter?</p>