"Per stirpes" is Latin for "according to the branch," meaning each branch of the family receives an equal share of a parent's estate or trust, according to Armstrong Law Offices. The share of any predeceased child is split equally among that child's children.
The intent of a per stirpes distribution is to allow the grandchildren to receive the benefit they would have gotten had their parent not passed away prior to receiving the inheritance. Spouses, who may have children unrelated to the deceased parent, are not considered when determining family branches.
A brief example: Parent A has children, B and C. Parent A specifies that her estate is to be equally divided between B and C, per stirpes. C dies first, leaving two children, C1 and C2. When A dies, B receives half of the estate. C1 and C2 each receive one-fourth of the estate, sharing equally the half that would have belonged to C.