✅ Answer:

1⃣ Muhammad ibn Isma'il ibn Bazi’ said: A man asked Imam Reza (peace be upon him) in my presence about a man who marries a woman temporarily (mut’a) and stipulates that she should not expect children from him, but later she gives birth to a child, and the man denies the child. The Imam strongly condemned this and said: How can he deny the child?!

The man asked: What if he suspects her? The Imam replied: You should only marry a trustworthy woman.

📚 Tahdhib, Volume 7, Page 269

Bazi’ narrates: A man asked Imam Reza (peace be upon him) about a temporary marriage where a man stipulates that he does not want children, but the woman later gives birth, and he denies the child!

The Imam firmly responded, saying: How can he deny the child?!

The man asked: What if he accuses her of unfaithfulness? The Imam said: You should only marry trustworthy women!

2⃣ Ja'far ibn Muhammad narrates from his father that a man came to the Messenger of Allah (peace and blessings be upon him) and said: I practiced coitus interruptus with my slave girl, yet she gave birth to a child!

The Prophet said: Even with a tied pouch, it can sometimes loosen! Then he attributed the child to the man.

📚 Qurb al-Isnad, Page 65

3⃣ Regarding a woman who remarries during her waiting period (‘iddah), Imam Baqir or Imam Sadiq (peace be upon them) said: They should be separated, and she must observe a single waiting period for both. If she gives birth six months or more after the second marriage, the child belongs to the second husband. If she gives birth in less than six months, the child belongs to the first husband.

📚 Tahdhib, Volume 8, Page 168

4⃣ Imam Baqir (peace be upon him) said: A man from the Ansar came to the Messenger of Allah (peace and blessings be upon him) and said: This is my cousin and wife. I know nothing but good about her, yet she gave birth to a child who is very dark-skinned, with wide nostrils, curly hair, and broad features, unlike anyone among my uncles or ancestors!

The Prophet asked the wife: What do you say? She replied: Since this man became my husband, no one else has touched me. The Prophet lowered his head for a while, then raised it and said to the man: Take your child with you.

4⃣ Yunus narrates that for a woman whose husband has been absent and she gives birth, Imam (peace be upon him) said: The child is not attributed to the man, and the woman's claim that her husband returned and impregnated her is not accepted if his absence is well-known.

📚 Al-Kafi, Volume 5, Page 490

5⃣ Qummi narrates: One of the companions wrote to Imam Baqir (peace be upon him) regarding a woman who committed fornication and became pregnant, and later the man married her. She gave birth to a child who greatly resembled the man. The Imam responded in his handwriting and seal: The child is illegitimate and does not inherit.

📚 Tahdhib, Volume 8, Page 182

6⃣ Sa’id al-A‘raj narrates: I asked Imam Sadiq (peace be upon him): A man marries an untrustworthy woman, and later she claims to be pregnant. The Imam replied: He should be patient and endure because the Messenger of Allah (peace and blessings be upon him) said: The child belongs to the bed (of the husband), and for the adulterer, there is only stoning.

📚 Tahdhib, Volume 8, Page 183

7⃣ Imam Sadiq (peace be upon him) said: If a Muslim, a Jew, and a Christian have relations with a woman during the same period of purity, the lineage of the child is determined by drawing lots, and the child belongs to the one chosen.

📚 Tahdhib, Volume 9, Page 348

✅ In Shia jurisprudence, there are numerous narrations from the Ahlul Bayt (peace be upon them) that clarify and determine lineage in various circumstances, including inheritance and financial support. Some examples are mentioned above. DNA testing is not considered valid or authoritative in this context, and lineage cannot be denied or financial support and inheritance withheld based on such tests.

It is clear from the narrations that both cases of denying lineage and affirming it are addressed within their respective contexts, and rulings are based on these narrations, not DNA testing.