When you make an estate plan, you are under no obligation to leave anyone anything. You are free to disinherit your children if you wish.
If you have valid reasons to disinherit someone, it is best to explain your reasons to them. If they do not find out until you have died, they may assume it was a mistake. Or that someone influenced you. It could lead them to contest the will, wasting time and money and delaying other beneficiaries from receiving what you left them.
What is a valid reason to disinherit someone from your will?
There is no legal definition of what constitutes a valid reason to cut someone out of your will. You are the one who makes that judgment. Here are a few reasons people have used in the past:
To protect them: You may prefer to cut your child out of your will if you do not want people knowing how much you left them. You could leave them things by other more private means.
You fell out with them: Children can do things that make you want to disown them. Yet time can heal differences, and people can change. Once you are dead, you cannot rewrite your will to put a child back in.
You want to incentivize them: You could tell your child that you are disinheriting them unless they change their ways. If one child has a gambling addiction, you might consider it a waste to leave them anything, as you know it will end up in the hands of the casino. However, it may be better to use a trust to achieve this. It gives them a chance to reform their ways and claim their inheritance after your death.
If you wish to disinherit someone, you are free to do so. Yet consider seeking legal help to find out more about how a trust can serve many of your aims better.