Short answer. Your own. For support owed to ascendants, descendants and brothers and sisters, only the separate property of the person obliged is answerable. The community or partnership advances it only if you have no separate property — and the advance is charged against your share at liquidation.
What the law says
only the separate property of the person obliged to give support shall be answerable provided that in case the obligor has no separate property, the absolute community or the conjugal partnership, if financially capable, shall advance the support, which shall be deducted from the share of the spouse obliged upon the liquidation
Family Code, Article 197 — Which Property Answers for Support. Read the full provision →
Who is in this category
The article covers support owed to legitimate ascendants, to descendants whether legitimate or illegitimate, and to brothers and sisters whether legitimately or illegitimately related. These are people you must support because of your own blood relationship to them, not because of the marriage. That is the reason the burden is placed on your separate property: your spouse did not take on your parents or your siblings by marrying you, and the common fund exists for the family the marriage created.
The community is a fallback with two conditions
Two things must be true before common property is touched. The obligor must have no separate property, and the community or partnership must be financially capable of advancing the support. So a spouse with exclusive assets cannot route the obligation through the common fund because that is more convenient, and a common fund already strained by the family's own needs is not required to stretch. The word the article uses is advance, which tells you the character of the payment before it tells you anything else.
An advance is charged back at liquidation
What the community pays is deducted from the share of the spouse obliged upon the liquidation. Nothing is settled at the time; the correction happens when the regime is wound up and the accounts between the spouses are drawn. That is the mechanism that keeps the arrangement fair to the other spouse across a long marriage — she may watch common funds go out for years and still not be the poorer for it at the end. It also means the arithmetic depends entirely on records nobody keeps unless they are told to.
Record what is paid, and from where
Since a deduction has to be computed one day, keep the support you provide traceable: pay it from an identifiable account, note who it was for, and keep the receipts for medical bills, tuition and the like. If you have separate property, expect to be asked why it was not used first. And be clear about which obligation you are performing — support for your own children with your spouse is a different matter, governed by different rules, and mixing the two in one account is what makes the eventual accounting expensive.