Apparently, when his mother died, Lewis Armistead gave custody of his son, Armistead Newton, to his sister, Cornelia Newton. Lewis later died in at Gettysburg. Armistead eventually disappeared and wasn't heard from again.
Cornelia also eloped with a army lieutenant Gore and had two sons fromthat relationship (see below).
FROM NOTES ON FAMILY HISTORY -- TRADITION AND FACT, AS REMEBERED BY ADELE M. MAYNARD. -- 1934
My great-grandfather, Gen. Walker Keith Armistead, was one of the first four graduates from West Point; an oil portrait of him hangs in the West Point Military Academy - I believe in the LIbrary. He fought inthe Seminole War, in Florida, and at the outbreak of the war with Mexico was appointed Gen. in Chief of the U. S. army in Mexico, but died of a heart attack the day he received the dispatches. Gen. Zachary Taylor was, I believe, appointed in his place. His son, Lewis Armistead (a young Lieutenant at that time) distinguished himself at the taking of a fortress at Chapultepec. Afterwards when in command of a small fort onthe Indian frontier, a large band of hostile Indians rode up to the Chief, took hold of his horse's forelock and turned him around, motioning forthe Indians to leave; they wer apparently so surprised that they did so. This was told my mother by a man (I think County Clerk) here in San Jose who was a soldier in the for at the time; - Louis Spitzer.
During the Civil War as Gen. Lewis Armistead, he led Pickett's Division at Gettysburg -- leading his men up a hill to take the Union batteries; he carried his hat on the point of his sword in order thathis men might distinguish him and follow him. He was badly wounded and carried by Union soldiers into the tent of Gen. Hancock (a close friend) where he died. Years before the Civil War, his young wife had died, leaving an infant son. My mother's father Maj. W. I. Newton was stationed at Fort Washita, Indian Territory (now Oklahoma), with him was the wife and infant daughter (my mother) Elizabeth Stanley; young Capt. Armistead brought his infant son to his sister -- the brother, Armistead Newton, was talented and Brilliant, but dissipated and worthless; he disappeared many years (about 50) ago; we have never heard what became of him, but he must be dead. The sister, Cornelia Love Newton, eloped with a wild young man, a Lieut. in the U. S. army, a gambler and a drunkard; she died, leaving two sons, Newton and James Gore; Newton is in a Sanitarium in southern California, the probably victim of his own and his father's sins; James is in San Francisco (1289 2nd Avenue) he has two sons and a daughter.