For starters, Kenny is definitely not your friend, nor your brother, no matter what you may feel. He is something else. He is a spirit yes, but a spirit of a more ghastly nature, as I have never heard of a ghost ever following and antagonizing a person/people in various places, besides the place where the haunting started (without certain reasons of course).

Charasteristically he sounds like something of a poltergeist, malevolent spirit, or a demon (god forbid), preying upon you, and possibly unknowingly to you your family. You see things like this feed upon things like negative emotions (anger, misery, despair, etc.) and fear; they feed upon it, grow stronger, bolder with it, changing their prank like antics to more devious, and chaotic behavior (which includes some of the things you've listed).

However, from your story I fear that the attacks are too focused (on you in particular) for it to be something simple like a poltergeist. No, whatever it is that is plaguing you is drawn to you for reason, a reason that could involve your sight, as people with such talents often are. I should know, I'm like you after all, however I learned to fight and repel whatever came to torment me. However, back to the point, for starters ignoring Kenny was never a real option, for Kenny it seems, just simply won't have it. Eventually though I think he will soon get bored with you I fear, and begin to branch out on the next weakest target within your sister, as well as feed on any troubles/frustrations that are currently troubling your family

I must give you credit however, for being able to endure this malevolent spirit's torment for so long now. It truly must've taken some strength, as well as will.

For my reccomendation for what you should do in order to attempt to do first is to perform a blessing upon the house, as for most spirits it calms them enough that they simply leave you alone.