title: Merged column doesn't display properly
body: <p>This is my first data frame df1</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID</th>
  <th>Name</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>1</td>
  <td>Sam</td>
  </tr>
  <tr>
  <td>2</td>
  <td>Mam</td>
  </tr>
  <tr>
  <td>3</td>
  <td>Dam</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>This is my second data frame df2</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID</th>
  <th>Parent ID</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>1</td>
  <td>4</td>
  </tr>
  <tr>
  <td>2</td>
  <td>5</td>
  </tr>
  <tr>
  <td>3</td>
  <td>6</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>This is my third dataframe df3</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>Parent ID</th>
  <th>Location</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>7</td>
  <td>New York</td>
  </tr>
  <tr>
  <td>8</td>
  <td>London</td>
  </tr>
  <tr>
  <td>9</td>
  <td>San Diego</td>
  </tr>
  <tr>
  <td>4</td>
  <td>Mumbai</td>
  </tr>
  <tr>
  <td>5</td>
  <td>Pataya</td>
  </tr>
  <tr>
  <td>6</td>
  <td>Canberra</td>
  </tr>
  </tbody>
  </table>
  </div>
  <pre><code>df4=pd.merge(df1,df2,on=['ID'], how='left')
  </code></pre>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID</th>
  <th>Game</th>
  <th>Parent ID</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>1</td>
  <td>Sam</td>
  <td>4</td>
  </tr>
  <tr>
  <td>2</td>
  <td>Mam</td>
  <td>5</td>
  </tr>
  <tr>
  <td>3</td>
  <td>Dam</td>
  <td>6</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I want to merge now the df5 which is giving me the invalid result</p>
  <pre><code> df5=pd.merge(df4,df3,on=['Parent ID'], how='left')
  </code></pre>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID</th>
  <th>Game</th>
  <th>Parent ID</th>
  <th>Location</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>1</td>
  <td>Sam</td>
  <td>4</td>
  <td>New york</td>
  </tr>
  <tr>
  <td>2</td>
  <td>Mam</td>
  <td>5</td>
  <td>London</td>
  </tr>
  <tr>
  <td>3</td>
  <td>Dam</td>
  <td>6</td>
  <td>San Diego</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I am not sure why it is selecting the first values instead of the common ones like the first merge</p>