Instead, Black Jack Randall fought on Culloden field as he had in the original timeline, and he died in his showdown with Jamie, leaving a pregnant wife behind who would continue the Randall line all the way to Frank in the 20th century.
Even Claire’s prophecy to Black Jack Randall that he would die at Culloden didn’t change his fate.
Sure, the father of the child was actually Randall’s brother, but that was likely always the case and it was simply not recorded in the history books.
Back when Claire first taunted him with the day of his death, I was convinced that it would be a loophole that would allow him to avoid his death and live on to menace Claire and Jamie.