Sam, Iris, and Tony are the children of Max, who is Leon's brother. Therefore, Sam, Iris, and Tony are Leon's niece and nephews. To Leon, Sam and Tony are his nephews, and Iris is his niece.

Fiona and Giles are the children of Leon. Since Leon is Max's brother, and Max is married to Ruth, who is Jake's sister, this makes Fiona and Giles Jake's niece and nephew. So, Fiona and Giles are Jake's niece and nephew, respectively.
Jake has a sister named Ruth, and Ruth is married to Max. Ruth and Max have three children, named Sam, Iris, and Tony. Max's brother, Leon, has two children named Fiona and Giles. Explain how Sam, Iris, and Tony are related to Leon. Also, how are Fiona and Giles related to Jake? Respond very briefly.