Legal Question in Wills and Trusts in California

A joint tenancy asset belonged to your Step-Mother [presuming she is the joint tenant with your Father], on the moment of his death. As such, it is not an asset of his estate and not subject to his Will terms. A Will may not have to be probated; that depends on the amount of the estate, whether there is real estate and so on. So, payment may be able to be made without a probate but again, that would depend on the estate and Will.

Can or must? If she didn't want to liquidate assets that were in the probate, she could probably use her own (ie jtwros) assets to pay the specific bequests (to do this formally, she could lend the cash to the probate estate.) But, if there are insufficient assets in the probate estate to pay the cash bequests, the jtwros assets, since they are not part of the probate estate, do not have to be used to pay the bequests. She can gift to you from them, but is under no obligation to do so.