ДНК S07E02 - Выпуск 875. Тест для внука №21

Six months ago, a widow with many children found out that her late husband could have a 10-year-old son from his mistress. But the boy's fathers are also attributed to the brother of the deceased man, allegedly the mistress was common. That's just the brothers' mother does not believe that her boys, exemplary family men, could give the 21st illegitimate grandson. So from whom did the mistress of the brothers give birth?