- Roelof Willemszen van Heerden (d. aft. 1667) m. bef. 1663 Willempje Thyssen (d. bef. 1690); Beverwyck, Brooklyn, N. Y.
- Mageltie Roelofsze (d. aft. 1703) m. Jan Hendrickszen Oosterom (1657aft. 1715); Midwout, Poughkeepsie, N. Y.
Walter Kenneth Griffin,
The Dutcher Family: To the Births of the Fifth Generation, with a Few Notes as to Subsequent Members,
and as to the Ancestors of Allied Families. Also, the Revolutionary Members, New York Genealogical and Biographical Record
30 (1909): 185-93, 249-58, gives an account of the early descendants of Roelof Willemszen and his brother, Jan. Male-line descendants
of the latter eventually assumed the surname Duytser or Dutcher, while all men identified as Ostrom or Oosterom came to descend from
Roelof. Griffin was unable to clarify the exact identity of Willem, however.
No further information on the ancestors of Willempje Thyssen is available at this time.
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