Your will does not necessarily have the final say on all assets. It is important how particular assets are handled. This can make a difference because houses, cars, retirement accounts and bank accounts can all be owned and transferred outside of the control of your will, according to the Daily Local News in "Asset titling can change the estate plan."
You might own a home with your second wife, as joint tenants with rights of survivorship. If you have a child from a previous marriage, you might want that child to get the house or your half of the ownership after you pass away. It does not matter if you express that in your will. When you pass away, the second wife will immediately become the sole owner of the home. That is how such joint ownership works.
An estate planning attorney can advise you on creating an estate plan that fits your unique circumstances and helps avoid problems with assets.
Reference: Daily Local News (June 26, 2018) "Asset titling can change the estate plan."