One might also make such a judgment with regard to  Susy. Or even Langdon.
Large families and untimely deaths were the norm in the  19th century. But
to
the point of your question, I do believe a case can be made  for Livy's
beneficial impact as editor in residence on Sam's literary work. The  tired
saw about
Livy lessening the vitality of Sam's writing just doesn't wash.  But by the
time of Livy's death, Sam Clemens was not the same man--his  bitterness came
to
dominate his thinking and his life. Resa Williams has done a  good treatment
of Livy & Sam, called "Mark and Livy--The love story of Mark  Twain and the
woman who (almost) tamed him."

David H  Fears