Isaac is a liar like dad.

Gen 26:7 says, "And the men of the place asked him of his wife; and he said, She is my sister: for he feared to say, She is my wife; lest, said he, the men of the place should kill me for Rebekah; because she was fair to look upon." The apple doesn't fall far from the tree. Isaac tells the same, "my wife is my sister" story that Abraham told twice. God rewardes Abraham each time he lied so maybe god thinks it is good to lie.