ДНК S06E57 - Выпуск 774. Женился сразу на двух?

The mother disliked her daughter because of her resemblance to her father, who went to another woman, married her, and she bore him a child. The daughter grew up and found her younger sister to inform about her existence, but she did not believe in the relationship. But why is the brother of the deceased father sure that he has two nieces?