The northern Indians have mixed with Dravidic peoples over the centuries & the Persians have mixed with Semitic & Old European (whose closest modern cousins would be the Basques) peoples.
The Nordics are not the direct descendents of the Aryans but are descendents of people who were cousins & therefore closely related to the Aryans, but not actually descended from the group known as Aryans. Remember: the Proto Indo-Europeans who are believed to have originated in southern Russia near the Caspian Sea branched out in many different directions. The group that migrated into Persia & India were known as Aryans, while the groups which migrated into Europe (& elsewhere) were a different branch (& branches) of the original group whose origins are believed to be near the Caspian Sea.
Remember also that groups of Proto Indo-Europeans migrated from the "homeland" into different directions at different times in history as well.