Legal Question in Wills and Trusts in California

Thanks for the additional information. I think I get it now.

If the sister who adopted your nephew is still alive, she's the mother for all legal purposes, and the sister who is the biological mother can't really get a guardianship - the sister who adopted the minor should file a response objecting to the petition stating that she's the mother and hasn't been declared as an unfit mother.

If, on the other hand, the sister who adopted your nephew is dead, and your nephew needs a guardian, then see a lawyer. You need to file a response to the petition describing all of the reasons why the biological mother shouldn't be guardian, including that her son was adopted away from her, etc. There is no designated form for this - your objections will have to be drafted, preferably by an attorney.

You could also file your own petition for guardianship. This page has a checklist of forms needed to file for the guardianship of a minor:

http://www.scscourt.org/self_help/probate/guardianship/guardianship_checklist.shtml