Yes, Digory Kirke is indeed related to the Pevensie siblings in C.S. Lewis’s The Chronicles of Narnia. Specifically, he is their uncle.
To delve a bit deeper, Digory Kirke first appears in The Magician’s Nephew, where he embarks on a significant adventure that leads to the creation of Narnia. In a way, he serves as a bridge between the origins of Narnia and the later stories involving the Pevensies. By the time of The Lion, the Witch and the Wardrobe, which is set many years after the events of The Magician’s Nephew, Digory has become an elderly professor, living in London and serving as the guardian of his nephew and nieces, including Peter, Susan, Edmund, and Lucy Pevensie.
Thus, while the Pevensies and Digory Kirke don’t interact extensively in the narratives, their familial connection enriches the backstory of Narnia and enhances the themes of legacy and adventure that run throughout the series.