My response:
Yes, your stepchildren can, in fact, force a probate action.
Despite the fact that the house was "always in your name", the fact remains that Nevada is a "Community Propery" State, and your deceased wife had a Community Property interest in the house from the date the two of you were married to until the date of her death.
Let's assume that on the date of marriage, the house was worth $100,000.00. That amount is your "separate property" and will always be yours. Let's further assume that from the date of marriage through the date of death, the house increased in value to $200,000.00 - - meaning, that there was a $100,000.00 appreciation in value. Likewise, you have a 1/2 interest in the appreciated value, or $50,000.00 of the "appreciated value."
That would leave $50,000.00 in her Estate. Upon her death, you would automatically obtain 1/2 of her Estate, or $25,000.00 of her share of the appreciated value of the house in her Estate. That would leave $25,000.00 of the appreciated value up for grabs in her Estate.
Your uncaring, greedy, stepchildren want that $25,000.00, and unless you refinance the house to pay them off, they will obtain a court order to have the house sold in order to get their share.
You should have protected yourself from the beginning with a Prenuptual Agreement, or a clause in her Will, that stated that all of her rights to real and/or personal property would have immediately, and 100%, reverted to you. But, you didn't, and now the wolves are knocking at your door, ready to huff, puff and blow your house down.
IAAL