Cousins Island was named after Englishman John Cousins (circa 1596–1682), who emigrated from Marlborough, Wiltshire. Cousins Island, along with Cousins River and Littlejohn Island, are named in his honor. For more detailed information, you can refer to sources like Wikipedia and DBpedia.
John Cousins played a significant role in the settlement of these areas during the 17th century, contributing to the early colonial history of the region.