Complex sentence: They are actually a kayastha Dutta family of Andul, who are descendants of Shri Purushottam Dutta, founder of the "Bharadwaja Gotriya Kannaujiya Dutta Family of Dakshina Rari".
Split into simpler sentences: They are actually the kayastha Dutta family of Andul, who are the "descendant of Shri Purushottam Dutta". Shri Purushottama Dutta was the founder of the "Bharadwaja Gotriya Kannaujiya Dutta Family of Dakshina Rari".