Short answer. It depends on the reconciliation. Article 920 of the Civil Code lists an attempt by one parent against the life of the other as a ground for disinheritance — but the statute specifically adds 'unless there has been a reconciliation between them.' If your parents reconciled, this particular ground may not be available to you.
What the law says
An attempt by one of the parents against the life of the other, unless there has been a reconciliation between them.
Civil Code, Article 920 — Grounds to Disinherit Parents and Ascendants. Read the full provision →
The ground and the reconciliation exception
Article 920(8) makes an attempt by one parent against the life of the other a sufficient cause for the child to disinherit that parent. This recognizes that an attack on one parent is deeply damaging to the family and to the child who witnesses or suffers from it. However, the statute contains an explicit exception: unless there has been a reconciliation between them. If the parents who were involved in the attack have genuinely reconciled, the child cannot invoke this specific ground — the victim's own choice to reconcile with the attacker forecloses it.
Why reconciliation between the parents matters
The exception reflects a deliberate policy choice. When the parent who was nearly killed chooses to reconcile with the attacker, the law respects that choice. The surviving parent's forgiveness is treated as a circumstance that removes the sting of the wrong for purposes of the testamentary right of the child. The child cannot invoke a wrong that the primary victim has chosen to overlook — at least not on this specific ground. The reconciliation must be between the parents, not between the testator and the attacking parent.
Other grounds may still apply
Even if the parents' reconciliation bars Article 920(8), the same events may support disinheritance on other grounds. If the attempted killing led to a criminal conviction for the attempt against your mother's life, then Article 920(2) may apply — conviction of an attempt against the life of the testator's ascendants covers an attempt against your mother if she is your ascendant. Article 920(2) does not include a reconciliation exception. Whether Article 920(2) applies depends on whether your father was actually convicted and on the specific relationship described in that provision.
Executing the disinheritance properly
Whatever ground you rely on, the disinheritance must be in a valid will that names your father and states the cause. Vague language or an unstated reason will not support the disinheritance. If you intend to rely on the attempted killing as grounds, you should identify the specific provision of Article 920 you are invoking, briefly describe the act, and note the relevant facts — particularly whether your parents reconciled and which sub-ground you believe applies despite that reconciliation. This allows the clause to be understood and defended if your father's heirs later challenge the will.