Yes, but by God alone. We can but ask Him to accept indulgences on their behalf. But we can certainly offer them with a definite conviction of their normal acceptance by God for those we love, even as we can share our goods in this life with more needy friends. This too is implied by the doctrine of the Communion of Saints.
Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty