In this question, I don't understand why the answer is "only the portion of the proceeds of sale due to the brother" when the statute in the question says that a creditor's judgment will "be a lien on the real property then owned or subsequently acquired by any person against whom the judgment is rendered." Wouldn't the property "then owned" by the brother be the property?

Please explain.

Question A mother owned Blackacre, a two-family apartment house on a small city lot not suitable for partition-in-kind. Upon the mother's death, her will devised Blackacre to "my son and daughter." A week ago, a creditor obtained a money judgment against the son and properly filed the judgment in the county where Blackacre is located. A statute in the jurisdiction provides: any judgment properly filed shall, for 10 years from filing, be a lien on the real property then owned or subsequently acquired by any person against whom the judgment is rendered. The son needed cash, but the daughter did not wish to sell Blackacre. The son commenced a partition action against the daughter and the creditor. Assume that the court properly ordered a partition by judicial sale. After the sale, the creditor's judgment will be a lien on all of Blackacre. B only a one-half interest in Blackacre. C all of the proceeds of a sale of Blackacre. only the portion of the proceeds of sale due to the brother