Short answer. Yes, in principle. Collateral relatives within the fourth civil degree of consanguinity or affinity may petition, and a sibling is second degree while a first cousin is fourth. But because you are not the offended party, your application must be accompanied by an affidavit covering the abuse and her consent to your filing.
What the law says
(c) ascendants, descendants or collateral relatives within the fourth civil degree of consanguinity or affinity
RA 9262, Section 9 — Who May File. Read the full provision →
What the law says
If the applicants is not the victim, the application must be accompanied by an affidavit of the applicant attesting to (a) the circumstances of the abuse suffered by the victim and (b) the circumstances of consent given by the victim for the filling of the application.
RA 9262, Section 11 — How To Apply. Read the full provision →
A sibling and a first cousin are both inside the fourth degree
Degrees are counted by steps up to the common ancestor and back down. From you to a sibling is two steps, so a brother or sister sits comfortably within the limit; an aunt, uncle, niece or nephew is three; first cousins are four, which is the outer edge. Second cousins fall outside it. The clause also says or affinity, so the same reach applies to relatives by marriage — a sister-in-law is within it. Ascendants and descendants are named separately in the same clause, without any degree limit attached to them.
Her consent is the part you cannot supply for her
The affidavit an applicant who is not the victim has to attach covers two things, and the second is the circumstances in which she consented to the filing. That requirement is not a test of whether she is frightened enough or has suffered enough. It reflects that the case will be hers to carry — hearings, service on the respondent, the consequences at home afterwards — and that no relative can weigh those for her. A woman may have entirely sound reasons for not being ready that she has told nobody, including you.
The section does not end at relatives
If the route through you is closed, others in the same list remain open, and none of them depends on her asking you first. Social workers of the DSWD or of the local government, police officers, the Punong Barangay, and her own lawyer, counsellor, therapist or healthcare provider each appear as separate categories. So does a pair of concerned responsible citizens of the city or municipality where the violence occurred who have personal knowledge of it. Any of these can be approached for advice about what they are able to do, whether or not a petition follows.
What you can do that does not require her signature
You can make the practical side easier without filing anything. The law directs barangay officials and court personnel to assist applicants in preparing an application, and law enforcement agents to extend assistance in cases brought to their attention, so the help exists before she decides. It also makes records of these cases confidential and penalises publishing a victim's identifying information without her consent. Keeping a private, dated note of what you have seen yourself — and where she can reach you at short notice — costs her nothing and keeps the option live.
Related provisions
- RA 9262, Section 10 — Where To Apply
- RA 9262, Section 13 — Legal Representation Of Petitioners
- RA 9262, Section 44 — Confidentiality