Short answer. Yes. Article 947 provides that a legatee or devisee acquires a right to a pure and simple legacy or devise from the moment the testator dies, and transmits that right to his own heirs. Dying before actually receiving it does not erase the right; it simply passes into your estate.
What the law says
The legatee or devisee acquires a right to the pure and simple legacies or devises from the death of the testator, and transmits it to his heirs.
Civil Code, Article 947 — The Legatee's Right Vests at Death. Read the full provision →
Your right vested the moment the testator died
Article 947 answers this by fixing the exact moment your right to the legacy was born. It provides that the legatee or devisee acquires a right to the pure and simple legacies or devises from the death of the testator, and transmits it to his heirs. Because you were named a legatee or devisee of a pure and simple gift, meaning one not subject to a condition or a term that had not yet arrived, your right to it existed from the instant the testator died, regardless of how much time passed afterward before the legacy was actually delivered to you.
That right transmits to your own heirs at your death
Because the right already existed and belonged to you from the testator's death, it forms part of what you own, and like any other asset you own, it passes to your own heirs when you die, even if you died before actually receiving physical delivery of the legacy. The article says this directly: the legatee transmits it to his heirs. Your heirs step into your position with respect to that legacy, entitled to claim it, because your right to it did not depend on you personally surviving long enough to collect it.
Why 'pure and simple' matters
The article specifies pure and simple legacies or devises, meaning gifts that are not conditional and not deferred to a future date or event. This distinction matters because a conditional or term-dependent legacy generally does not vest in the same immediate way; the legatee's right may depend on the condition being fulfilled or the term arriving first. For an unconditional, immediately effective legacy, though, vesting happens right away at the testator's death, which is why your death afterward does not defeat it.
What this means for your heirs
Because your right to the legacy vested at the testator's death and did not depend on you personally being alive to collect it, your heirs can claim the legacy on your behalf as part of your own estate. They step into the entitlement you already had, rather than having to establish some new, independent claim of their own against the testator's estate.