Complex sentence: It is possible that the Jutes are a related people to the Geats and a Gothic people as it is mentioned in the "Gutasaga" that some inhabitants of Gotland left for mainland Europe (the Wielbark site in Poland is evidence of a Scandinavian migration).
Split into simpler sentences: It is possible that the Jutes are a people related to the Geats and a Gothic people. The "Gutasaga" mentions that some inhabitants of Gotland left for mainland Europe (the Wielbark site in Poland is evidence of a Scandinavian migration).