I Am Interested In the Paranormal

a close family friend was dying of bone cancer that had spread everywhere and couldnt be treated. he couldnt remember anything right and was always out of it but anyway he walked out of the house for some fresh air i guess and he looked at his truck, he appeared to be confused so he asked his wife why my auntie was sitting in his driver seat, there was no one there. he didnt even remember she had died two years earlier. weird 😦

It is highly unlikely that this is your sister.
Ghosts are formed by people who have some sort of strong reason to linger, whether it is regret, need of revenge, etc.
Furthermore, "ghosts" are not the souls of people who have departed (except in very rare cases), they are a metaphysical imprint.
These "ghosts", depending on why they are still around, can become dangerous if they are left to stay within the physical realm. They become less "sentient" and more and more of whatever their reason to linger is.
If they are lingering due to a need of revenge, that need will start to possess them and they become less like their living self.
If this is a ghost, you need to be careful, especially if it is a ghost that is lingering around you, as it could become increasingly dangerous.

You don't pass up the opportunity to annoy a sibling for eternity.

Like what?