The time travel ones aren't really paradoxes, you're just making assumptions about the nature of time travel which we don't actually know anything about
It could be that when you travel back in time and make some sort of change like bumping off your Grandparents you cause a new 'timeline' to form which continues separately from the 'timeline' where you didn't kill your Grandparents, you then won't be born in that particular 'timeline'.
Or there's the infinite universes theory where to travel back in time you actually travel to a parallel universe, again in that universe when you kill your Grandparents you won't actually be born - it doesn't matter though because you are still born in the original universe...
Edit - oops, too slow