If children, or other lawful descendants holding property or legacies subject to be collated, should renounce the succession of the ascendant, from whom they have received such property, they may retain the gift, or claim the legacy to them made, without being subject to any collation.

If, however, the remaining amount of the inheritance should not be sufficient for the legitimate portion of the other children, including in the succession of the deceased the property which the person renouncing would have collated, had he become heir, he shall then be obliged to collate up to the sum necessary to complete such legitimate portion.