Legal Question in Real Estate Law in California

There are all sorts of mistakes in what you describe. This is why professionals need to be involved in real estate transfers. For tax reasons your father should never have put you or your sister on title and instead put it in a trust with the two of you as beneficiaries. The next problem is that unless the property was already in a trust with your father as trustee (with or without your mom) or the original deed to your mom and dad was as "Joint Tenants" he had no legal right to transfer her half of the property just because she died. Even if he was trustee or it was held in Joint Tenants, he was powerless to transfer her half until he recorded proper documentation of her death in the chain of title. Unless he did all that, her community property right to half ownership needed to pass to your father by trust, or in a probate proceeding by will or intestate succession (if there was no will or trust, by intestate succession you, your father and your sister would each be entitled to 1/6 of the property (1/3 each of mom's 1/2) regardless of any deed by your father. As for signing the deed, a copy doesn't matter. What was recorded with the County Recorder is what matters. It also doesn't matter if the grantee(s) sign a deed because only the grantor needs to sign it to be effective. That said, if your name and your sisters name were on signature lines, that is ANOTHER mistake that clouds title. Long story short, you and your dad and sister now have a really messed up chain of title that may well be uninsurable by title companies if and when you or anyone you might grant it to tries to sell it to any third-party. If your dad dies before it is straightened out, it will be an even bigger mess, because now you'll still need to probate your mom, and then your dad's interest in the property will have to be probated separately. You need to see a lawyer in person.