A spokeswoman for the Attorney General's Office said the sentence will be referred to the Court of Appeal, where three judges will decide whether or not the sentence is unduly lenient.
Having carefully reviewed this case, the Attorney General, Dominic Grieve QC MP, has decided to refer the sentence of Lewis Gill to the Court of Appeal for review.
The case will in due course be heard by three Court of Appeal judges who will decide whether they should increase the sentence.
More top news
A split in conditions for the coming few days
Relatives of Becky Watts have said her death was the "most undignified end to a beautiful life full of promise".
Some sunshine is breaking through the wintry weather as Spring arrives.