I am raising a relative as my child and am in the process of gaining guardianship of her. Another relative may contest it. I have raised her since she was 6 weeks old; she is now three. I love as if she were my own child. Is there anything I could do to prepare for this potential legal challenge?

As always so far as the courts interest is concerned there is the best interest of the child that is suppose to be held as the cornerstone of the decision. In your case there is already a track record. Is the challenge being issues because of a fear they won't get to see the child once you have custody ? If that's the case maybe you could offer a visitation agreement. How close is the relative offering the challenge.. Grand Parent or other blood relative ?

From what I understand, you have had her since she was 6 weeks old therefore she KNOWS you as mom and has her stability with you.
A Judge is most likely to look at that alone as 'the best interest of the child'. The court wouldn't uproot her because another person wants her. They would have to prove that you are not fit or some valid reason she should not be with you.

Thank you for your advise. The challenge may come from my mother-in-law. She seems to think that her son and I are not "fit" to raise her, although so many people have told us what a happy and wonderful child she is. I think that she is worried that if we gain guardianship of her, I MAY TAKE her away. She doesn't have to worry because doing that would just hurt my daughter and I don't want to do anything that would hurt my little one, no matter what differences grandma and I have. She has had medical and dental insurance since she was six weeks old and we are using no public assistance. We have her parents blessing; I am pursuing this guardianship in order to be legally prepared to help her, if she needs it (ie. Receiving medical treatment in a life threatening situation like a car accident or cancer diagnosis and not withholding it while trying to contact the biological parents). She deserves to be loved by both sides of her family. Anyway, thanks for the advise all.

Fortunately what in the eyes of your mother in law are unfit very likely have nothing to do with what legally constitutes unfit.

You have an advantage over anyone else in a custody (guardianship) dispute because you've acted as the child's parent for a substantial period. The law on nonparent custody is found in Family Code Section 3041:

" (a) Before making an order granting custody to a person or
persons other than a parent, over the objection of a parent, the
court shall make a finding that granting custody to a parent would be detrimental to the child and that granting custody to the nonparent is required to serve the best interest of the child. Allegations that parental custody would be detrimental to the child, other than a statement of that ultimate fact, shall not appear in the pleadings. The court may, in its discretion, exclude the public from the hearing on this issue.
(b) Subject to subdivision (d), a finding that parental custody
would be detrimental to the child shall be supported by clear and
convincing evidence.
(c) As used in this section, "detriment to the child" includes the
Harm of removal from a stable placement of a child with a person who has assumed, on a day-to-day basis, the role of his or her parent, fulfilling both the child's physical needs and the child's psychological needs for care and affection, and who has assumed that role for a substantial period. A finding of detriment does not require any finding of unfitness of the parents.
(d) Notwithstanding subdivision (b), if the court finds by a
preponderance of the evidence that the person to whom custody may be given is a person described in subdivision (c), this finding shall constitute a finding that the custody is in the best interest of the child and that parental custody would be detrimental to the child absent a showing by a preponderance of the evidence to the contrary.

(e) Notwithstanding subdivisions (a) to (d), inclusive, if the
Child is an Indian child, when an allegation is made that parental
Custody would be detrimental to the child, before making an order granting custody to a person or persons other than a parent, over the objection of a parent, the court shall apply the evidentiary standards described in subdivisions (d), (e), and (f) of Section 1912 of the Indian Child Welfare Act (25 U.S.C. Sec. 1901 et seq.) and Sections 224.6 and 361.7 of the Welfare and Institutions Code and the placement preferences and standards set out in Section 361.31 of the Welfare and Institutions Code and Section 1922 of the Indian Child Welfare Act (25 U.S.C. Sec. 1901 et seq.).

Although the statute pertains to objections to a guardianship by a parent, the presumption of section 3041 would have all the more force if the contest is only between two nonparents.

Technically the grandmother has no standing to object to the guardianship anyway. Simply being a grandmother does not mean that she is treated as a parent. So, I think you will do fine. Of course, the grandparent may seek some visitation rights (which have nothing to do with custody) and she would need to file a petition for grandparent visitation, and that may result in some access time being awarded as well. To simplify things you may just want to offer the grandmother some visitation time and let the court make orders on it in the guardianship.

Thank you for your response cadillac59. I don't think that there will be any "visitation" issues. My daughter goes to see grandma two or three times a week and sometimes on the weekends. I also appreciate the legal information you provided. Thanks again.

If I read you right (because you never answered the question) the child is your niece and one of the bio parents is your husband's sibling?

Otherwise your mom-in-law is only a "grandmother" through her son is married to you. In that case, she would have no legal standing whatsoever.

As the others have pointed out, I see no reason the courts would wrest the child from you. But to avoid the expense of a court battle, I would reassure grandma, that you have no intention of interfering with her relationship with the child.

ScottGem, she is a niece to both my husband and myself. I am related to her mother and my husband is related to the father. She is a "third cousin" to both of us. The problem is that his mother objects to me taking her to see my family (who live out of state), although the little one spends the majority of the time with his family (who live in the same city). So to keep the peace, my family flys in to see us, instead of us travelling out of the state to see them.

I'd say that is bending over backwards to not take her to see your family. You and your daughter should be able to have visits with your family with whatever is convenient at the time where it is you go there or they come to you.
I'd just keep reassuring her that no matter what she is grandma and she will get to continue her relationship with her grand daughter.

If the other party plans on lawyering up, then you'd better too. Otherwise, save your money. Generally stability in the child's life is the prime compelling factor in cases like these. You say you've been raising this child since she was 6 weeks old and is now 3. That being the case, you are essentially the child's parent, in spirit if not biologically. As long as you are adequately providing for this child's physical and emotional needs and are not subjecting her to any abuse or endangerment I don't honestly see any judge awarding guardianship to anyone else. The only possible sticking point would be the nature of your relationship and the other party's relationship to the child. For example, if you are an aunt and the contesting party is a biological parent, that might come into play.