Short answer. Yes, generally. Article 206 of the Family Code lets a stranger who gave support, without the knowledge of the person legally obliged to give it, claim reimbursement from that person. The one exception is if it appears the stranger gave the support without any intention of being reimbursed.
What the law says
When, without the knowledge of the person obliged to give support, it is given by a stranger, the latter shall have a right to claim the same from the former, unless it appears that he gave it without intention of being reimbursed.
Family Code, Article 206 — Reimbursing a Stranger Who Gave Support. Read the full provision →
A stranger who supported your relative can generally claim it back
Article 206 addresses exactly this situation: when, without the knowledge of the person obliged to give support, it is given by a stranger, the latter shall have a right to claim the same from the former. If you were legally obliged to support the relative and someone else stepped in and gave that support without your knowledge, the article gives that stranger a right to be reimbursed by you — the person the obligation actually belonged to.
Why "without your knowledge" is part of the rule
The article specifically addresses support given without the knowledge of the person obliged to give it. This is what distinguishes the situation from one where you knew support was being given on your behalf and, implicitly or explicitly, allowed it to happen. Article 206 is built around a stranger who acted independently, filling a gap you were not even aware existed, rather than someone acting with your awareness or arrangement.
The exception: support given without intent to be reimbursed
The right to reimbursement is not absolute. The article states the claim exists unless it appears that he gave it without intention of being reimbursed. If the circumstances show the stranger meant the support as a gift — with no expectation of ever getting it back — the right to reimbursement does not arise. Whether that intention existed is a factual question, to be judged from how the support was given and what was said or understood at the time.
What this means if you are being asked to reimburse someone
If someone is now asking you to reimburse them for support they gave your relative, the two things Article 206 puts at issue are whether you were, at the time, obliged to give that support yourself, and whether the stranger's own intention was to be reimbursed rather than to give the support as a gift. Both points are about the specific facts of what happened — what was said, why the support was given, and whether reimbursement was ever discussed or assumed at the time.