Whose daughter is Sita - Janaka or Ravana?

Whose daughter is Sita - Janaka or Ravana? 
We all have heard about the Indian epic Ramayana and I am sure, majority of us have read it or have heard its story. We all know that it's a story of god Rama and goddess Sita, and how Rama married Sita, and his father asking him to spend 14 years in forest. In forest, abduction of Sita by Ravana and the war between Rama and Ravana. We all know that Sita was daughter of King of Mithila, Janak. Devi Sita was discovered in a groove of ploughed field by King Janaka.

But you know that this is only according to Valmiki Ramayana. There are not less than 60 versions of Ramayana and majority of versions claim that Ravana was father of Sita. Let's have a look and know on what basis they claim that Sita was daughter of Ravana.

1. According to The Adbhuta Ramayana narrates: Ravana used to store the blood of sages he killed in a large pot. The sage Gritsamada was practicing penance to acquire the goddess Lakshmi as his daughter. He stored milk from Darbha grass and purified it with mantras in a pot so that Lakshmi would inhabit it. Ravana poured the milk from this pot into his blood pot. Mandodari is frustrated seeing the evil deeds of Ravana, so she decides to commit suicide by drinking the contents of the blood-pot, which is described to be more poisonous than poison. Instead of dying, Mandodari gets pregnant with the incarnation of Lakshmi due to the power of Gritsamada's milk. Mandodari buries the foetus in Kurukshetra, where it is discovered by Janaka, who named her Sita.

2. The Devi Bhagavata Purana says: When Ravana wants to marry Mandodari, Maya warns him that her horoscope indicated her first-born would destroy her clan and should be killed. Ignoring Maya's advice, Ravana buries his first child by Mandodari in a casket in Janaka’s city, where it is discovered and grew up as Sita.Jain adaptations of the Ramayana like Vasudevahindi, Uttara-purana, and others also state that Sita is the daughter of Ravana and Mandodari, and is abandoned when she is prophesied to be the cause of the end of Ravana and his family.

3. In the Malay Seri Rama and the Indonesian-Javanese Rama Keling, Ravana wants to possess Mandodari, the mother of Rama, but instead marries a pseudo-Mandodari, who looks like the real one. Rama's father has a union with this pseudo-Mandodari, resulting in the birth of Sita, who is nominally Ravana's daughter.

4. According to the Ananda Ramayana, king Padmaksha had a daughter named Padma - an incarnate of the goddess Lakshmi. When her marriage is organized, Rakshasas (demons) kill the king. The grief-stricken Padma jumps into fire. Ravana discovers her body, which had turned into five jewels, in the fire and takes it to Lanka sealed in a box. Mandodari opens the box and finds Padma inside it. She advises Ravana to cast off the box containing the ill-fated Padma, who led to the doom of her father. When the lid of the box is closed, Padma curses Ravana that she will return to Lanka and cause his doom. Ravana buries the box in the city of Janaka, who discovers Padma and brings her up as Sita.