1,863. Brothers Who Obligate a Widow in Yibum

Yibum v’Chalitzah 1:6

If a man has a brother, even if the brother is illegitimate or idolatrous, whether the brother is an adult or a minor, so long as his head and the greater part of his body came into the world before the man died, he obligates the widow in yibum. If the brother is the child of a servant or a non-Jewish woman, he is not halachically the deceased’s brother and he doesn’t obligate the widow in yibum. This is true even if the brother was born Jewish; since his mother wasn’t Jewish when he was conceived, he is not halachically the brother of the deceased.

Yibum v’Chalitzah 1:7

Brothers who share just the same mother are only considered brothers under the laws of mourning and of witnesses. When it comes to the laws of inheritance and of yibum and chalitzah, maternal brothers are immaterial. Fraternity is based strictly on paternity.