The bodies were discovered by neighbours who called police.
When police reached the spot, they found the family home locked from the outside.
"In the initial investigation, it looks like a case of suicide. Although the family has raised doubts about some people, no proof has been found yet. Besides a mark from the noose, no other injury marks can be seen on the bodies of both girls," Noida SP Arun Kumar Singh said.
The girls' parents told police they are suspicious of a relative who had been living with them along with his wife.
The parents told police the relative had "stained the reputation" of their older daughter, and that he had been threatening to kill both the sisters for some time.