Here’s what I have for those two families; I took this verbatim from the notes of my Great-Aunt Cornelia Dockstader Fonda, written in 1940. Your suspicion appears to be right about some errors in your information.
Douw Jellise Fonda was born at Schenectady, N.Y. August 22, 1700 and baptized there on September 1, 1700, the son of Jellise Fonda and Rachel Winnie Fonda. On October 29, 1725 (First Dutch Church of Schenectady, N.Y.) He married Maritje Vrooman (Vroman) (September 11, 1699 – June 30, 1756) a daughter of Adam Vrooman (Schenectady Massacre) and Grietje Heemstraat Vrooman.
1. Jelles, b. Schenectady, NY b. 3-24-1727 bp. 4-4-1727 d. 6-23-1791, became Major (War of the Revolution); married Jeanetje Vrooman, a grand-daughter of Adam Vrooman.
2. Adam, died young
3. Adam, died young
4. Margrietje, b. Schenectady 11-10-1737 married Barent Myondertse Hemple
5. Adam, b. Schenectady 12-26-1736, died at Caughnauaga NY 11-8-1808, married Neeltje Breese, a daughter of Hendrick Breese and Wyntje Van Vechten Breese.
6. John, b. Schenectady 3-8-1740, died at Caughnauaga NY 2-19-1815, married Angelica Hansen.
Adam Fonda, fifth child of Douwe Jellese Fonda and Maritje Vrooman Fonda, was baptized at Schenectady October 26, 1736 – he was their third son to be named Adam. He died at Caughnauaga N.Y. on Nov. 8, 1808. On March 14, 1759 he married Neeltje Breese (3-18-1739 – 12-12-1820) a daughter of Hendrick Breese and Wintje Van Vechten Breese (Stone Arabia Lutheran Church Records).
1. Maria, b. 5-12-1761, d. 4-11-1864, married John Veeder, a son of Johannes Veeder and Catherine Mabie Veeder.
2. Henry Adam, b. August 20, 1766, died September 9, 1828, married Hester Mabie (1766 – 1840) on February 14, 1790.
3. Douw Adam, b. 12-30-1774, d. 7-4-1855, married Lavina Breese (1766 – 1857)
4. Wyntie (Lavina), b. 5-26-1768, d. 12-14-1851, married ---.