Good luck! First right answer get brianliest!
3 the grand father is one of them i think
OMG OMG OMG WAIT WAIT WAIT IS IT 3 tickets?
I'm changing my answer last minute so i hope you didn't explain already but i think i hopefully maybe figure it out. It's 3 tickets because the grandfather is also a father and then the father is also a son so it would be a grandpa, his son, and his grandson.
...am i right????