I was just wondering what the California law is about the following.
After my mother died my ex sister in law at the day of the funeral approached my father to sign things over to her, I believe he did? Then re recently got married and the lady talked my father into signing things over to her. As my fathers only living desendents, my brother and myself, what are our rights? Do we have a say so over this? This all took place while my father was grieving and I just want to know my rights.

Thank you

I take it your father is still alive?

Just have him sign everything over to you and your brother.

Question: What do you mean by sign it over? Did he give his house to sister-in-law, and then wife, or just had them take over it while retaining onto rights?

Nope, as long as he is of sound mine, he can sign over anything he has to anyone he wants.

When you mom died, if her will left you anything then you should have gotten that. If she did not have a will, or if she had one and did like most people and leave it to your spouse, your dad inherited everything.

If he remarries without a will, his new wife could inherit everything, you can try to sue in probate if this happens,

But he can give everything he owns to a stanger and move to MN and raise goats, it is his to do with as he pleases.

If he latter dies with a will, you may attempt to fight over property in probate if you wish.

And I gues what "things did he sign over to your ex sister in law, bank accounts, cars, houses, boats. Sign over insurance policies.
Perhaps he signed over power of attorney, perhaps he signed funeral papers she brought up from the funeral director.
You need to ask him about it. But again he has the right to tell you to mind your own business also.

And basically except to talk to your dad about it, and see what happened, you don't have any rights if he is mental competent to care for hisself.