Two women who assisted him in aborting the foetus were also arrested.
The three were produced before the court which promptly remanded them to judicial custody.
The 15-year-old grand daughter and her younger brother were staying with the grand father who, according to Thirukoilur all-women police was sexually abusing the girl for the past three years.
The local people coming to know of the issue alerted the village officer of Thirukoilur who informed the all-women police that took him into custody along with his two women accomplices - a retired woman nurse and another woman.
Police charged him under Section 6 (Punishment for aggravated penetrative sexual assault), 5 (aggravated penetrative sexual assault), 5(j) (whoever commits penetrative sexual assault on a child), 5(j)(ii) (makes a child pregnant as a consequence of sexual assault), and 17 (punishment for abetment) of the Protection of Children from Sexual offences (Pocso) Act, 2012.