doppelgangers as ghost?

I was biking with my dad just like the old days we traveled about a hour away from our house, once we were tired we headed back but 30 minutes later I see 2 people behind us looking similar to Eddie and Gabbie And I told my dad "hey look it's my favorite youtubers" as he stopped and looked back saying "I don't see anybody" I was confused as they passed by were these doppelgangers as ghost and how did I see then but my dad didint?