Hove MP Peter Kyle (Labour) told a Commons debate how Jane Clough's killer Jonathan Vass was able to cross-examined her family.
Vass was jailed for life for stabbing nurse Ms Clough in Blackpool in July 2010 on her way to work.
He was arrested outside her parents' house the day after the murder.
Mr Kyle said Vass was on his way to either murder his baby child, Jane's parents, or both.
The killer had started demanding parental rights over his child from behind bars, he said.
"The child he would have, by all likelihood, murdered himself if only he had had the opportunity," the MP added.
The MP told a Commons debate how several of his constituents who suffered domestic violence found abusers were using the family court system to continue their torment.
But he added: "If there is one example that sums up the sheer horror of abuse and its continuation in the family court, it is that of Jane Clough."
A family member started adoption proceedings in 2011 to break the link with Vass.
But the MP, who has spoken with Ms Clough's family as part of his research, said they experienced a legal system "stacked" in favour of the killer.
The would have had to sell their house to cover the costs without free help from a law firm.
Vass represented himself at the hearing, Mr Kyle said, adding: "The man who brutally murdered their sister, their daughter, would be cross-examining them.
"Jane's sister told me that she simply cannot find the words to do justice to the brutalising effect this had as the court date approached.
They were "stunned" to discover the hearing was by video-link due to concerns for his safety.
Vass asked personal questions and asked Jane's sister what would she tell the child about him.
"To her husband, he asked 'what makes you think you can be a dad to my daughter'?
"The trauma meted out by the family court process is simply inhuman. This family had suffered enough."
An MP has said it was "inhuman" that a murderer who killed his former partner tried to use the family courts to gain access to their baby.