'Half brother' in the Bible

Then Jotham ran away to Beer and lived there to escape from Abimelech his half-brother.

He did this so the violent deaths of Jerub-Baal's seventy sons might be avenged and Abimelech, their half-brother who murdered them, might have to pay for their spilled blood, along with the leaders of Shechem who helped him murder them.

It happened afterwards that Absalom the son of David had a beautiful sister whose name was Tamar, and Amnon [her half brother] the son of David was in love with her.

Later, her brother Absalom asked her, "Has Amnon, that brother of yours, raped you? Then keep quiet about your half-brother for now, my sister. Stop taking this so personally." From that time on, Tamar lived in continuous desolation within her brother Absalom's house.