Yup. Plus he bought that ranch before marriage so that's his. May have to give up something he bought after marrying her, or perhaps get a deal where he purchases a house for her+the kids.
Lot of these older celebs didn't get prenups so I'm impressed by Costner here. He would be fine regardless since he's filthy rich but imagine less successful actors from that era getting fukked up due to no prenup. Not to mention the athletes out here who have money but aren't preparing for retirement, when those NBA/NFL/etc checks aren't coming in.