Short answer. Article 104 of the Family Code has each community's capital, fruits, and income determined by proof under the rules of evidence when the liquidations of two or more pre-Code marriages happen at the same time. Where it is unclear which community a property belongs to, it is divided in proportion to each community's capital and duration.
What the law says
Whenever the liquidation of the community properties of two or more marriages contracted by the same person before the effectivity of this Code is carried out simultaneously, the respective capital, fruits and income of each community shall be determined upon such proof as may be considered according to the rules of evidence.
Family Code, Article 104 — Overlapping Communities from Multiple Marriages. Read the full provision →
What the law says
In case of doubt as to which community the existing properties belong, the same shall be divided between the different communities in proportion to the capital and duration of each.
Family Code, Article 104 — Overlapping Communities from Multiple Marriages. Read the full provision →
When this article actually applies
Article 104 is written for a specific situation: two or more marriages of the same person, both contracted before the effectivity of this Code, where the community properties from those marriages are being liquidated simultaneously. Both conditions have to hold — the marriages predate the Family Code, and more than one liquidation is happening together rather than one estate having already been settled separately before the other is opened.
Tracing each community's own capital, fruits, and income first
The article's first move is evidentiary: the capital, fruits, and income belonging to each community are to be determined based on whatever proof is available, weighed according to the ordinary rules of evidence. This is not a formula applied blindly — it calls for actually establishing, marriage by marriage, what capital each community started with and what income or fruits are traceable to it, before any division happens.
The proportional fallback for what cannot be traced
Where tracing genuinely fails and there is real doubt about which community a property belongs to, the article supplies a fallback: the property is divided between the communities in proportion to the capital and duration of each. A community with more starting capital, or one that existed longer, receives a proportionately larger share of whatever property cannot be definitively traced to one marriage or the other.
Why records from both marriages matter here
Because the article leans first on proof and only falls back to proportional division when doubt remains, records showing when each marriage began, what each community's capital consisted of, and how any income or property developed over time are central to how the liquidation actually resolves. This is a documentation-heavy process, and it is worth working through the specifics with a lawyer experienced in liquidating overlapping marital property regimes.