Michael Pearce, 33, from Nelson, Caerphilly, was jailed for the manslaughter of his girlfriend's six-week-old son in July.
Solicitor General Robert Buckland has now referred the case to the Court of Appeal after a series of complaints.
Judges are expected to consider the sentence in October.
Pearce's trial at Newport Crown Court heard how he battered baby Alfie with a shoe and a plastic bottle while his mother Donna Sullock, from Cardiff, went on her first night out since giving birth.
The pair had become friends while she was six months pregnant, and later became a couple.
The magistrate's son had denied murder and manslaughter but was convicted of the lesser charge after nearly 36 hours of deliberation.
Judge Mr Justice Baker said Alfie died as a result of Pearce inflicting multiple blunt force injuries on the child.
The court heard Pearce began to display "obsessive behaviour" towards Ms Sullock and asked her to give him a child weeks into their relationship, which she had refused.
In his summing up, Mr Justice Baker said: "It may well be that due to your denials we may never know whether you were motivated by jealousy as a result of Donna's refusal to have your child earlier that evening."
A man jailed for killing baby Alfie Sullock will have his nine-year sentence reviewed by the Court of Appeal over concerns it is too lenient.