To determine the legitime of a forced heir when all forced heirs are of the first degree, the division of the forced portion is made by heads.
When representation occurs for purposes of forced heirship, the division is made by roots among those qualifying as forced heirs or being represented. Within each root, any subdivision is also made by roots in each branch, with those qualifying as forced heirs by representation taking by heads.
Nevertheless, if the fraction that would otherwise be used to calculate the legitime is greater than the fraction of the decedent's estate to which the forced heir would succeed by intestacy, then the legitime shall be calculated by using the fraction of an intestate successor.
La. C.C. § 1495.1