In the original timeline, Carolyn Preston married Henry Wallace and the two had a daughter named Amy Preston. She also had a child with Benjamin Cahill by the name of Lucy Preston. Wallace got Carolyn to start smoking which caused her to become gravely ill.
In the altered timeline, Lucy, Wyatt Logan, and Rufus Carlin prevent all deaths on the Hindenburg. Because of this, Henry Wallace marries Elizabeth Merrick, granddaughter of a Hindenburg survivor Irene Doehner. In this timeline, Wallace and Carolyn never meet, resulting in Amy Preston never being born, Carolyn becoming well because she never started smoking, and Lucy finding out that Henry Wallace was never her biological father. (“Pilot”)
Later, Carolyn reveals to Lucy that her biological father is Benjamin Cahill. Carolyn later also reveals that not only is Benjamin a Rittenhouse member, but so is she. (“The Red Scare”)