It depends on where you live. In my province the entire estate passes to the spouse.

This came up in my family when an uncle didn’t want his adult step kids inheriting his house. It would have gone to his wife to then be divided between all of her children after her death. He had to write a will for bypass his wife and leave it to his bio children.

Meanwhile where my MIL lives step children have to be included in property division. All children of a couple are to inherit equal shares. A loophole exists where you can leave land to only one child. People have been known to buy cheap plots of land to give to their step children.

Always best to have a will because laws can be weird.