____________________________
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                       ____________________________|
                      |                            |
                      |                            |____________________________
                      |                                                         
 _John WILLIAMSON ____|
|                     |
|                     |                             ____________________________
|                     |                            |                            
|                     |____________________________|
|                                                  |
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|                                                                               
|
|--Thomas Nicolas WILLIAMSON 
|  (1530 - 1602)
|                                                   _Henry THRELKELD ___________
|                                                  | (1399 - 1452)              
|                      _Lancelot Edward THRELKELD _|
|                     | (1435 - 1493)              |
|                     |                            |_Margaret Alice THORNBURGH _
|                     |                              (1402 - 1493)              
|_Isabel THRELKELD ___|
  (1510 - 1532)       |
                      |                             _John DERATCLIFFE __________+
                      |                            | (1426 - 1485)              
                      |_Elizabeth RATCLIFFE _______|
                        (1462 - 1520)              |
                                                   |_Ann FENWICK _______________
                                                     (1430 - 1513)