Casper's uncles as humans

Though casper tells kat that he died of pneumonia. the comics never really reveal how he or his uncles died. as to your question the only one we ever see in human form is casper he regains his human form for a short time towards the end of the film


the comics also never refer to the ghostly trio as his uncles they could simply be brothers or cousins

"Touchdoooooooooooooooooooooooooooooown Auburn"

When you play Casper the Playstation game, when you are going around Whipstaff there is a portrait on the wall of the 3 uncles and what they looked like as humans. Casper is from 1800s / early 1900s so they are wearing attire for that era

I wonder what his uncles' unfinished business is? No way of knowing I guess.