Short answer. The insolvent co-guarantor's share is spread among everyone else, including you. Article 2073 says that when a co-guarantor who should contribute is insolvent, his share is borne by the others, including the paying guarantor, in the same proportion. So you do not absorb it alone - it is divided across all the solvent guarantors.
What the law says
If any of the guarantors should be insolvent, his share shall be borne by the others, including the payer, in the same proportion.
Civil Code, Article 2073 — Contribution Among Co-Guarantors. Read the full provision →
A paying guarantor can seek contribution
When several people guarantee the same debtor for the same debt, and one of them pays, the law does not leave that payer to shoulder the whole burden. Article 2073 provides that the one among them who has paid may demand of each of the others the share which is proportionally owing from him. This right of contribution is what lets you turn to your co-guarantors and recover their proportional parts of what you advanced. Your payment benefited all of you by extinguishing the guaranteed debt, so the cost is meant to be split, not dumped entirely on whoever happened to pay the creditor first.
An insolvent guarantor's share is shared, not dropped
The trouble comes when one co-guarantor cannot pay his part. The article answers this squarely: if any of the guarantors should be insolvent, his share shall be borne by the others, including the payer, in the same proportion. So the missing share is not simply lost, and it does not fall on you alone. It is redistributed across everyone who can pay — the solvent co-guarantors together with you — each taking on a proportional slice of it. The result keeps the loss fair: the insolvency of one is absorbed collectively rather than punishing the person who stepped up to pay.
The right only arises in two situations
Contribution under this article is not automatic. The provision states that it shall not be applicable, unless the payment has been made by virtue of a judicial demand or unless the principal debtor is insolvent. So you can claim from your co-guarantors either where you paid after being sued on the guaranty, or where the principal debtor himself is insolvent. If you paid the creditor voluntarily while the debtor was still solvent and no suit had been brought, the article's contribution right — and with it the sharing of the insolvent's portion — does not come into play. The trigger conditions matter as much as the sharing rule.
What it does not do
This right lets you recover each co-guarantor's proportional share; it is not a way to collect more than that from any of them. Your first and best target usually remains the principal debtor, since a guarantor who pays steps into the creditor's shoes against the one who actually owed the money. The redistribution of an insolvent's share also depends on genuine insolvency, not a mere reluctance to pay. And the proportions follow your arrangement or, absent one, an equal division among the guarantors. Kept within these limits, the article ensures the guarantor who paid is made whole as fairly as the group's circumstances allow.