Short answer. No, and this one is unusually severe. Where a gift is made on condition that the heir provide for the testator or someone else in his own will, the Code voids the disposition itself — not merely the condition. The jewellery would fall to be dealt with as property the will never disposed of.
What the law says
Any disposition made upon the condition that the heir shall make some provision in his will in favor of the testator or of any other person shall be void.
Civil Code, Article 875 — Disposicion Captatoria. Read the full provision →
What the law says
Impossible conditions and those contrary to law or good customs shall be considered as not imposed and shall in no manner prejudice the heir, even if the testator should otherwise provide.
Civil Code, Article 873 — Impossible and Unlawful Conditions. Read the full provision →
What the law says
A will may be revoked by the testator at any time before his death. Any waiver or restriction of this right is void.
Civil Code, Article 828 — A Will Is Always Revocable. Read the full provision →
The whole gift falls, not just the condition
Read Article 875 against the ordinary rule and the difference is stark. Article 873 provides that Impossible conditions and those contrary to law or good customs shall be considered as not imposed and shall in no manner prejudice the heir, even if the testator should otherwise provide. — the offending condition is struck out and the heir keeps the gift. Article 875 goes the other way: Any disposition made upon the condition that the heir shall make some provision in his will in favor of the testator or of any other person shall be void. Void, and the disposition is what is void. You cannot take the jewellery and simply ignore the promise.
Why the Code singles this out
The condition is an attempt to reach into a will that does not exist yet and belongs to somebody else. Article 828 makes the point on its own: A will may be revoked by the testator at any time before his death. Any waiver or restriction of this right is void. So even if you accepted the jewellery and wrote the clause your aunt wanted, nothing would stop you revoking it the following week, and your cousin would have no remedy. Rather than tolerate a bargain the law makes unenforceable and then police the deception, the Code refuses the disposition outright.
What is not caught
The article speaks of a disposition made upon the condition. A testator who leaves you her jewellery and separately expresses the hope that it will one day go to your cousin has imposed no condition, and that gift is unaffected — the wish is simply a wish, which you may honour or not. Everything therefore turns on how the clause is actually framed, so the words matter more than the family's understanding of what she intended. Note too that Article 872 forbids any charge, condition or substitution on the legitime at all, so a clause of this kind reaching a compulsory heir's legitime is doubly ineffective.
Where that leaves the jewellery
A void disposition disposes of nothing, so the property is treated as though the will had said nothing about it. Article 960 provides that legal succession takes place with respect to the property of which the testator has not disposed — meaning the jewellery goes to your aunt's legal heirs under the intestate rules, which may or may not include you, depending on which relatives survived her. Before anyone acts on the clause, have the exact wording read by counsel, and do not sign an undertaking about your own future will in reliance on it.
Related provisions
- Civil Code, Article 875 — Disposicion Captatoria
- Civil Code, Article 873 — Impossible and Unlawful Conditions
- Civil Code, Article 872 — But Never on the Legitime
- Civil Code, Article 828 — A Will Is Always Revocable
- Civil Code, Article 960 — When Intestate Succession Applies