Charles Spurgeon Commentary Judges 8:18-19

"Then said he unto Zebah and Zalmunna, What manner of men were they whom ye slew at Tabor? And they answered, As thou art, so were they; each one resembled the children of a king. And he said, They were my brethren, the sons of my mother: as Jehovah liveth, if ye had saved them alive, I would not slay you." — Judges 8:18-19 (ASV)

Then said he unto Zebah and Zalmunna, What manner of men were they whom ye slew at Tabor? And they answered, As thou art, so were they; each one resembled the children of a king. And he said, they were my brethren, even the sons of my mother:

In the East, there is much greater affection between those who are the sons of one mother than between those who are only sons of one father.