Yevamos 11:1

If a couple had sexual relations out of wedlock – whether she acted willingly or he coerced her – they are permitted to marry.  [He is permitted to marry her close relatives.] If one seduces or coerces a married woman, he is liable to the penalties prescribed by the Torah. One may marry a woman coerced or seduced by his father or by his son; Rabbi Yehuda prohibits one from marrying a woman coerced or seduced by one’s father.

Yevamos 11:2

Let’s say that a woman converted to Judaism and her sons converted along with her. Later, they married and one of them died. In such a case, the surviving sons do not perform yibum or chalitzah. This is true even if one brother was conceived before the mother converted and born after, and the other brother was conceived and born after the mother converted. The same rules apply when a female servant and her son are freed at the same time.