The concept of an inappropriate birth or marriage that defies culturally expected norms.
Key passages
Wis 3:16–19

But children of adulterers will be unable to reach maturity, and the seed of unlawful intercourse will perish. For even if they become long-lived, they will be reckoned as nothing and without honor at the end of their old age. Even if they die quickly, they have no hope or comfort in the …

Wis 4:6

For children begotten from lawless sleep are witnesses of wickedness against their parents when they the parents are tried.

Sir 23:22–23

So also a woman who leaves her husband and presents him with an heir from another man. For first of all, she has disobeyed the law of the Most High, and second, she has committed an offense against her husband, and third, she has committed adultery by prostitution; she presented children …