If you are concerned that certain beneficiaries or others will attempt to contest certain provisions that you have made, you can include a "no contest clause" in your estate planning documents which states that if a beneficiary contests provisions of your estate plan, then they will not be able to inherit from you.
Please note that laws vary by state and change from time to time regarding whether a "no contest clause" can be enforced. If you currently live in or move to a state where a "no contest clause" is unenforceable, it is possible that this provision may not be binding.