He savagely stabbed both to death at their family home in Myrtle Avenue, Totton, on February 25 this year.
At Winchester Crown Court this morning the judge told Marsh, 22, that although he accepted he had had a mental disorder at the time, the jury
rejected his defence that the voices he claimed to have heard in his head were impossible to ignore.
Dressed in a dark grey pinstripe suit and white open-necked collarless shirt Marsh listened impassively as the judge told him his crimes were "horrendous". But he nodded and said thank you before
being taken down from the dock.
The two life terms will run concurrently and the judge warned Marsh that he would not automatically be released once he served 26 years and he would only be freed when he is considered to no longer
be a threat to the public.
In sentencing Mr Justice Tim Holroyde told Marsh his crimes had been made worse by the vulnerable nature of his victims.
He said: "Lili by reason of her age but also Stephanie for the simple reason that you waited until she was soundly asleep before attacking her."
The judge added that the scene of "brutality" he created has left a terrible lasting memory for Stephanie's mother and sister, who found the bodies.
He said: "For a mother and sister to find a loved one in such a position is truly appalling.
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