SOURCE: Eye of the Storm
Claire informs Geillis she's traveled through the stones 3 times and Geillis wonders how she accomplished it if not with blood. Claire admits she doesn't know but says she suspects it is someone on the other side calling you to them.
SOURCE: Dragonfly In Amber
Jamie and Claire set out to stop the Jacobite Rising by intercepting the Bonnie Prince Charlies mail. When they find out he is looking for backing from creditors. Jamie and Claire thwart and lucrative deal with the Comte St. Germain leaving the Prince broke.
Jamie and Claire return to Scotland believing they have prevented the Bonnie Prince but he manages to gain support and money and arrives on Scotland's shores.
Despite all Jamie and Claire attempted to do to stop the Rising and the culminating Battle of Culloden they were unable to change history.
Can history be changed?
SOURCE: The Hail Mary
Claire believed BJR was Frank's direct ancestor but after the dual with Jamie was left unable to father children. Claire believed they could change history and because of BJR's injury Frank wouldn't be born.
However, Claire discovers Alex Randall and Mary Hawkins conceived a child. Because of Alex's illness he wouldn't be around for his family. Alex asked Jack Randall to marry Mary and give his child a name. This made Alex the direct ancestor of Frank which either was history working itself out or a family secret.
This change seems to have no effect on the timeline though it is possible Alex was always Frank's ancestor.