A woman took her own life after the Northern Territory Government took her baby daughter into care, the Royal Commission into the Protection and Detention of Children in the NT has heard.

A woman, known as DT, gave evidence before the commission on Wednesday, and said that after her son and his partner had their second daughter removed, they took part in a series of counselling and rehabilitation programs, but never got their baby back.

"It was a cycle for them to be going through over and over," she said.

They did everything the Department of Children and Families (DCF) asked them to do, she said.

"She [her son's partner] thought she couldn't do any more to be strong to get those kids back."

DT said her son's partner took her own life the day her son returned from rehabilitation.

"She used to tell me a lot, 'I can't take this anymore because I am crying so much'," she said.

"It really hurts me, too.

"She tried to become very strong, you know, for those kids."

DT also said the department had told her the woman's daughters would attend her funeral, but it never happened.

Baby was removed while parents were away

In her evidence, DT said child protection had agreed that her son and his partner could go away for weekends as long as she was available to look after the baby.

But she said that one weekend while they were away, child protection workers came and removed the baby from her care.

"I said to her, those two are out because they were allowed to have some time off on weekends because I am here to take care of the baby," DT said she told a female worker.

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"She was all fine and all good about that, and then she rang the other fella, he was the guy from DCF also.

"He then came up to home and he said, 'no there's an order from the DCF mob up in Darwin to say we have to take the child'.

"I felt so heartbroken because the baby was fine with me."

DT said she, her son, and his partner asked the department the following Monday why the alleged agreement had been broken.

"But then they decided or made all these arrangements to say they were going to send the baby to a carer," she said.

DT said they saw both daughters once or twice after that but they were never returned to the family's care.