Nicholas Brendon wanted everything to go to his brother and nothing to go to his ex ... this according to a handwritten will submitted to court by his brother.

Documents were filed Monday by Nicholas' brother, Kelton Schultz, seeking to administer the probate estate pursuant to the terms of a handwritten will.

The docs note Nicholas didn't have a spouse or children -- and there's no estimate for what the estate is worth at this time.

Along with Kelton, three other people are listed as potential beneficiaries of the estate ... Nichola' parents, Robert and Kathleen, and Nicholas' ex-girlfriend Sarah Marker.

However, a handwritten note is attached to the filing as well which reads simply, "My will. Sarah gets nothing kel gets everything. He can figure it out.”

As you know ... Nicholas passed away back in March of cardiovascular disease. Acute pneumonia and a previous heart attack were listed as contributing factors in his death.

Nicholas was a series regular on "Buffy the Vampire Slayer" ... playing Xander Harris on all 7 seasons of the hit show.