What is the ruling regarding the marriage of a man and a woman who, after having five children, discovered that there was a forbidden suckling relationship between them in the past, and how should the children act in this situation?

The questioner is not to be blamed for this marriage, as it predates her existence. The sin lies with the father and uncle if they were aware of the prohibition. The prohibition applies if it is confirmed that the father of the questioner was suckled by her grandmother five times or more during the first two years of life. In this case, the marriage is null and void due to the existence of a prohibited degree of relationship, as the mother would then be the father's niece through suckling. Allah Almighty says: (And your foster-sisters) and the Prophet (peace be upon him) said: "What is prohibited by lineage is also prohibited by suckling." The parents must separate immediately upon becoming aware of this. It is not permissible for either of them to allow the other to enjoy marital relations; otherwise, they would be committing adultery. The questioner must advise them gently. The children born before the knowledge of the prohibition due to suckling are attributed to their father.