In South Park Darlington UK there are two absolutely enormous redwood trees, each with about four or five other trees (younger redwoods) growing out from them at the bottom.
It is normally the Coast Redwood (Sequoia sempervirens) rather than the Giant Redwood (Sequoiadendron giganteum / Giant Sequoia / Wellingtonia) that sprout from the base of an existing tree.
Photo by smiler5