Before and After is one of the better episodes, and according to that, Tom didn't start with Kes until after B'Elanna died... But Kes knew before hand about what she had to gain from a loving partnership with Tom, would she claim jump heading the Klingon off at the pass, as easily as also how to make sure that B'Elanna and Janeway didn't die during the first minute of the Year of Hell.
B'Elanna or Kes? If Kes had stayed, and B'Elanna had lived, who would have been making babies with Tom in Season Seven?
B'Elanna or Kes? If Kes had stayed, and B'Elanna had lived, who would have been making babies with Tom in Season Seven?