Since per stirpes distributions will automatically pass through equally amongst a Beneficiary's heirs, there's no need to update any of your documents.

Is per stirpes the default?

Most will default to either a “per stirpes” designation or a “per capita” designation. ... A per stirpes designation means that if one of your IRA beneficiaries is deceased, the deceased person's children will receive his or her share.

Is per stirpes a good idea?

So, attorneys should use the term “per stirpes” only in the context of descendants and not go rogue by using “children, per stirpes” or “siblings, per stirpes.” Also, it is a good idea to use a proper definition of “per stirpes” because the term varies in different jurisdictions.