Short answer. No. The Civil Code bars an illegitimate child from inheriting ab intestato from the legitimate children and relatives of the father or mother, and bars those relatives from inheriting from the illegitimate child in the same way. The barrier runs both directions and applies specifically to intestate succession.
What the law says
An illegitimate child has no right to inherit ab intestato from the legitimate children and relatives of his father or mother; nor shall such children or relatives inherit in the same manner from the illegitimate child.
Civil Code, Article 992 — The Barrier Between Legitimate and Illegitimate Relatives. Read the full provision →
A barrier that runs in both directions
Article 992 is often called the "iron curtain" rule because it cuts off intestate succession between an illegitimate child and the legitimate side of the family, and it does so symmetrically. The illegitimate child has no right to inherit ab intestato from the legitimate children and relatives of the parent — a grandparent, an aunt, a legitimate half-sibling. The reverse is stated just as plainly: those legitimate relatives likewise cannot inherit from the illegitimate child. Neither side reaches across the line into the other's intestate estate.
It only closes the intestate route
The rule is specifically about succession ab intestato — inheritance that happens by operation of law when there is no will directing otherwise. It does not reach into what a person can do voluntarily during life or through a will. A grandparent who wants to provide for an illegitimate grandchild, or an illegitimate child who wants to leave something to a legitimate relative, is not stopped by this article from doing so by will or by donation; what the article closes is the automatic, no-will channel of intestate succession.
The relationship this cuts, and the one it does not
Article 992 concerns the illegitimate child's relationship with the legitimate children and relatives of the parent — it does not touch the child's succession rights from the parent directly, which are governed by other rules on an illegitimate child's own share of the parent's estate. The barrier is specifically about crossing from the illegitimate child into the legitimate branch of the family, and vice versa, not about the direct line between parent and child.
What this means when an estate is being settled
If you are an illegitimate child and a legitimate relative of your parent dies without a will, this article is the reason you are not automatically counted among the intestate heirs, however close the relationship in life. If you are administering an estate and an illegitimate relative is asserting an intestate claim against a legitimate decedent's estate, checking whether any will or other voluntary disposition exists is the relevant next step, since this article addresses only what happens in its absence.