The eighth-grader died on Sunday at the Dhaka Medical College Hospital, three days after being knifed by a youth near her school.
The 14-year-old girl’s family said Obayed, who worked at a tailoring shop in Dhaka, had been ‘harassing’ Risha over phone for some months.
They suspect he stabbed the girl on Wednesday on a foot over-bridge near the school at Dhaka’s Kakrail.
The case opened by the family accuses Obayed of the murder.
Police detained Obayed’s sister Khadija Begum and brother-in-law Khademul Islam on Monday night from their home at Dinajpur’s Birganj Upazila.
Khadija told reporters that his brother came to visit them on Thursday and left hours later. He has been untraceable since then, she said.
She claimed they knew nothing about Obayed being sought for a murder in Dhaka.