The mother of a teenager who fell pregnant to a 40-year-old man has told the ACT Supreme Court she only learned he was the father of her grandchild when he turned up on her doorstep after the child was born.

The man, who is now 58, is facing charges of committing acts of indecency and rape, over the relationship which began in the 1990s, when the girl was 14.

The pair went on to have three more children, before splitting.

The court heard allegations that the now 32-year-old woman fell pregnant twice while she was still underage, although the first pregnancy ended in a miscarriage.

She has denied suggestions from the man's lawyers that the first pregnancy was the result of a sexual relationship with someone else.

Yesterday the court heard that the man believed she was 17, and did not ask her age until after their first child was born.

But the woman said she told him she was only 14 after their second encounter.

The woman's mother today told the court her daughter had been afraid to tell her she was pregnant the first time.

"We were in a shopping centre," she said.

"[She] told me and then ran away because she was scared about how I would react.

"She was very anxious. She wouldn't say much, I just assumed it was someone at school."

The woman said her daughter had referred to someone who lived in their block of flats.

"But she wouldn't tell me his name," the mother said.

The woman told the court she did not know the man was the father until he turned up on her doorstep, after the birth of the child.

Man cooked for girl 'because mother burned things'

Documents shown to the court revealed the circumstances were reported to Family Services by the mother during a doctor's consultation.

The mother told the court she had no memory of that.

The court earlier heard that the man had often cooked for the girl because her mother had trouble cooking, and burned things.

Today her mother denied that, saying she had often been unwell, but always kept a freezer full of lamb and a drawer of potatoes, so her daughter could make her own food.