Short answer. As a rule, no. No descendant may be compelled in a criminal case to testify against parents and grandparents. There are two exceptions: where the testimony is indispensable in a crime against the descendant, or in a crime by one parent against the other.
What the law says
No descendant shall be compelled, in a criminal case, to testify against his parents and grandparents, except when such testimony is indispensable in a crime against the descendant or by one parent against the other.
Family Code, Article 215 — A Descendant Cannot Be Compelled to Testify Against Parents. Read the full provision →
The protection is against compulsion, not against testifying
Read the verb carefully. What the article forbids is compelling the descendant; it does not silence a child who chooses to speak. A son who wishes to testify against his father may do so, and the article gives the father no right to stop him. What it means is that the child cannot be made to — no subpoena, no threat of contempt, no pressure from a prosecutor can force the choice. The decision belongs to the descendant, and the law's concern is that it not be extracted from him.
Who is covered, and where
The protection runs upward through the bloodline, covering testimony against parents and grandparents, and it belongs to any descendant, adult or child. Its setting is limited: it applies in a criminal case. A civil action between family members is not within this sentence, however painful the testimony sought. And the direction matters — the article shields a descendant from being compelled against an ascendant, which is not the same as a general family privilege covering every relative in every proceeding.
Two exceptions, both narrow
The first is where the testimony is indispensable in a crime against the descendant. The qualifier is strict: not merely useful or convenient, but indispensable, and in a case where the descendant is the one wronged. The law will not let the family bond become a shield in a prosecution for what was done to the child himself. The second covers a crime by one parent against the other, where a child is often the only witness to what happened inside the home. Outside these two situations the protection stands.
Raise it when the subpoena arrives
In practice this is asserted at the moment the descendant is called, so the time to get advice is when the summons or subpoena is received, not on the day of the hearing. Be clear about which of the two exceptions the other side may invoke and why, since that is the argument the point will turn on. And be equally clear with the child that the choice, where the rule applies, is genuinely theirs — pressing a child to invoke it is its own kind of compulsion, and the court will not be blind to it.