.. 1 King Edward I of England I (1239 - 1307)
.. + Alianore de Castile (1240 - 1290)
.... 2 Elizabeth Plantagenet (1282 - 1316)
.... + Humphrey de Bohun VIII (1276 - 1322)
...... 3 Margaret de Bohun (1311 - 1391)
...... + Hugh de Courtenay (1303 - 1377)
........ 4 Edward de Courtenay (1332 - 1368)
........ + Emmeline d'Auney ( - 1372)
.......... 5 Hugh Courtenay (1358 - 1425)
.......... + Philippa l'Arcedekene (1386 - )
............ 6 Hugh Courtenay
............ + Margaret Carmino
.............. 7 Elizabeth Courtenay (1447 - 1510)
.............. + John Trethurffe (1451 - )
................ 8 Reynold Tretherffe ( - 1597)
................ + Margery Nanskill (1497 - )
.................. 9 Margaret Tredurf (1538 - 1576)
.................. + Thomas Beauchamp (1534 - )
.................... 10 Dorothy Beauchamp (1562 - )
.................... + Thomas Brown (1553 - 1591)
...................... 11 Edward Brown ( - 1610)
...................... + Jane Leids (1578 - 1610)
........................ 12 Ann Brown (1595 - 1669)
........................ + Adam Hawkes (1605 - 1672)
.......................... 13 Susanna Hawkes (1633 - 1696)
.......................... + William Cogswell (1620 - 1700)
............................ 14 Susanna Cogswell (1658 - 1701)
............................ + Benjamin White (1626 - 1723)
.............................. 15 Ann White (1685 - 1772)
.............................. + Peter Boylston (1673 - 1743)
................................ 16 Susanna Boylston (1709 - 1797)
................................ + John Adams (1691 - 1761)
.................................. 17 John Adams (1735 - 1826) 2nd President of the U.S.
.................................. + Abigail Smith (1744 - 1818)
.................................... 18 John Quincy Adams (1767 - 1848) 6th President of the U.S.
.................................... + Louisa Catherine Johnson (1775 - 1852)

Note that John Quincy Adams is descended from Edward III through his mother.