Short answer. Yes, if they were given in consideration of that marriage. Everything stipulated in a marriage settlement in consideration of a future marriage, including donations between the prospective spouses made in it, is rendered void when the marriage does not take place.
What the law says
Everything stipulated in the settlements or contracts referred to in the preceding articles in consideration of a future marriage, including donations between the prospective spouses made therein, shall be rendered void if the marriage does not take place. However, stipulations that do not depend upon the celebration of the marriages shall be valid.
Family Code, Article 81 — Effect of the Marriage Not Taking Place on Settlements. Read the full provision →
The marriage is the reason, so no marriage means no gift
A settlement made before a wedding is not an ordinary contract standing on its own feet. Its whole premise is the marriage that is meant to follow. So the law provides that everything stipulated in it in consideration of a future marriage is rendered void if the marriage does not take place. The gift is not merely revocable at the donor's option, to be undone by a court if he changes his mind; it falls away because the condition it rested on failed. That is why an engagement that ends is not treated as a completed transfer with regrets attached.
What counts, and what does not
The provision reaches what was stipulated in the settlement or contract, expressly including donations between the prospective spouses made therein. It is not a general rule that every present exchanged during an engagement must be returned. A gift given for a birthday, a car bought as a favour, or money handed over to help with a business is not a donation by reason of marriage simply because the couple were engaged when it changed hands. What the document says the gift was for, and whether the marriage was its stated consideration, is the dividing line.
The clause that survives the cancelled wedding
The article ends with a saving rule: stipulations that do not depend upon the celebration of the marriages shall be valid. A single deed can therefore have two fates. Terms that were always contingent on the wedding fall; terms the parties would have agreed to regardless, such as an acknowledgment of an existing debt, a recognition of who owns a particular asset, or an obligation towards a child already born, continue in force. Reading a settlement after a broken engagement is largely an exercise in sorting its clauses into those two piles.
What to do with the paperwork now
Retrieve the signed settlement and any deed of donation and read them for the words of consideration, because that is where this is decided. Where land or a registered vehicle was transferred, the transfer will sit in a public register and someone must take steps to correct the record; the underlying gift being void does not clean up the title by itself. Keep proof of what was actually delivered and when, and of the fact and date the marriage was called off. Take all of it to a lawyer together rather than a single page at a time.