Short answer. Yes, the other co-heirs can demand partition even before the condition is fulfilled, but they must give sufficient security to protect the conditional heir's potential share. The partition will be treated as provisional until it becomes clear whether the condition is met or can no longer be met.
What the law says
the other co-heirs may demand it by giving sufficient security for the rights which the former may have in case the condition should be complied with, and until it is known that the condition has not been fulfilled or can never be complied with, the partition shall be understood to be provisional
Civil Code, Article 1084 — Conditional Voluntary Heirs. Read the full provision →
The rule under Article 1084
Article 1084 of the Civil Code draws a clear line: the conditional heir cannot demand partition while the condition is still pending, because their right has not yet vested. But the rest of you — the heirs whose shares are unconditional — are not stuck waiting indefinitely. You may proceed with partition as long as you give sufficient security to protect whatever rights the conditional heir might eventually enjoy. This security safeguards the conditional heir so that if the condition is later fulfilled, they can still receive what they would have been entitled to.
The partition is provisional, not final
Even after the other co-heirs proceed with partition, it does not become final right away. The statute is explicit: "the partition shall be understood to be provisional" until one of two things happens — it is established that the condition has not been fulfilled, or it becomes clear that the condition can never be complied with. Only at that point does the partition acquire the character of a completed division. This provisional status means that if the condition is later satisfied, the arrangement may need to be revisited to account for the conditional heir's share.
What counts as sufficient security
The Civil Code does not prescribe a specific form of security — the standard is that it be sufficient to cover the conditional heir's potential rights. In practice this could take the form of a bond, a pledge of assets, or a cash deposit, depending on what the parties agree or a court approves. The adequacy of security will depend on the value of what the conditional heir might receive if the condition is met. If you and the conditional heir cannot agree on what is sufficient, the court can intervene to determine the proper amount and form.
When the waiting ends
Two events terminate the provisional character of the partition. First, if it becomes certain — whether by the passage of time, the death of a relevant person, or some other definitive fact — that the condition will never be fulfilled, the other co-heirs are free and the security can be released. Second, if the condition is actually fulfilled, the provisional partition must be revisited and the conditional heir given their rightful share, with the security serving to guarantee this. The law avoids leaving all heirs indefinitely in limbo; it balances protection of the conditional heir against the legitimate interest of the rest of the family in settling the estate.