This is accurate as far as I know. Some bits may be wrong or if you can help fill in the gaps mail me.

I know the picture one was prettier but it was getting too wide so have replaced it with a less pretty one. Hopefully it's still understandable.

                                                      /4. Helen MacFarlane
       / 2. Charlie -----3. Cat the Mongoat ---- 4. Rachel
      |
      |        / 2. Gemma -------------| 3. Alex
      |       |                         \ 3. Charlie C
      |       | 2. Hel --------------- 3. Adam
1. Julie      | 2. Rhian
        + ----| 2. Laura                 / 3. Helen W
1. El J       | 2. Sam------------------| 3. Ros
      |       |                         | 3. Jodie
      |       |                         | 3. Katherine
      |       |                          \ 3. Catherine
      |        \ 2. Sarah
      |
      + -----2. Jamie Jr. (the hypothetical)
      |
1. Jamie
      |        / 2. Richard S        / 3. Claire
      +-------|      + -------------| 3. Chloe
1. Tee        | 2. Abby                  / 3. Anne
               \ 2. Libby --------------| 3. Edain
                                        | 3. Eleanor
                                         \ 3. Katherine