What steps do we need to take next for my sister and brother-in-law to move out of the house since mom has passed?

In California, if you show as the owners of record of the property, you would initiate an unlawful detainer case to have them evicted.

You need to send them a notice to quit and file a complaint for eviction in District Court.

Send a notice in writing requesting them to leave, refer to the Will and legal documents you have giving you the power to do this if that does not work you may have to do a legal eviction (unlawful detainer action). Either way it sounds like you would be best served if you have an attorney assisting and advising you on what you can and can't do.

You will need to file a petition for probate to get yourself appointed executor of the estate; during the course of the probate the court will issue the two you title to the property; at that time you can list the property for sale, and obtain a court order removing your brother from the premises if he will not go voluntarily. Obtain yourself a probate lawyer to assist you in this proceeding.

If they won't move, you'll have to evict them.

You need to evict him.

You and your brother could evict your sister.

The only way to legally require your sister and brother-in-law to move is to open a probate and have the court formally appoint you the executor of your mother's estate. Your mother's naming you in her will is not sufficient authority; you must also obtain court approval to be the executor. The probate is also necessary in order for the house to be transferred to you and to your brother. I strongly suggest you contact a probate lawyer for assistance in this matter. Best of luck to you.

Since the house was left to both of you, she has a right to the house just as much as you. You can not sell the house us you both agree to do so.

It depends on how the title on the deed to the house reads. If your mother's name is on the title (and not as a trustee or part of the title of a trust), then to take legal steps, you need to at least be court?appointed as the executor (or "personal representative"). If so, you will have one page orders called Letters Testamentary (or Letters of Administration, if your mother died without a will). Such is a court order that authorizes you and your brother to act on the estate of your mothering. This authority includes being able to sign a deed transferring the house out of your mother's name to you and your brother. If the deed on the house shows a trust as the owner of the house, being held for your mother's benefit and use, then the governing trust documents probably specify who is or should be the current trustee. If you and your brother are the title owners on a deed to the house that has been recorded in the real property records of the county where the house is, then you can take steps to evict your sister. If the house has not yet been deeded into your names, then the executor (or "personal representative") or the trustee, as the case may be, may take steps towards evicting your sister from the house. If your sister will not voluntarily vacate the house on your request, then you may evict her through the 'unlawful detainer' process. This begins by posting on the front door of the house a notice (with legal 'bells and whistles'). In it, it specifies that if they do not leave, then an expedited court trial (within 5?12 days) will be held and the court may order eviction. I've tried such a case for a property owner. The judge ordered the occupants to leave the property. It was the dead of winter. It was frigid cold (below zero temperatures at night). The occupants and their two little children were ordered to be out of the house within 48 hours of the judge ruling that they had no legal right to be or remain in the house.

If your sister and her husband won't move out voluntarily, you can obtain a court order forcing them out. Or you can work out a deal with your sister to continue to live in the house and pay rent to you and your brother.

You will need to formally evict them through a landlord tenant proceeding. Need to give them a notice to, quit and if they ignore it you will have to take them to court.

Your question cannot be answered without knowing whether your sister is voluntarily leaving or not. If she is, it should be relatively easy. If she is not, then eviction proceedings may be necessary. That could certainly have a strain on your relationship, and whether to do this, and how, would be a consideration.