Hi!

This may sound really odd but I have experienced being a ghost myself. Guess trauma put me there.

Anyhow, the way you describe your ghost he too does not seem to have it all together.

Could be he is trying to show some kind of trauma with the blood thing.

That some thought the eyes were green and your sister blue could be a shift, I know someone who has those kind of eyes, one parent has green eyes, the other blue-gray and so the person can sort of have shifting eye color as one thinks its ice blue and someone else see the green in it.

When I was a ghost I was seemingly attached to more than one person, this too a family.

You could try contacting a medium who will help the ghost to move on or try it yourself, there are prays and such one can do.

Even though it has been giving people a fright it has not hurt anyone which I think is in his favor, despite the seeing of the blood. So maybe no need to be so frighten of him as one initially thinks one need to be.