Anthony Price, in a mid-70's novel, has one of his characters ironically describe the WWI British Army as "the scum of the earth, led by the fool of the family".
The first Duke of Wellington (Arthur Wellesley) once described the British Army as "The scum of the earth, enlisted for drink ...", then went on to say, "... But see what fine fellows we have made of them!" The quote is obviously a reference to Wellington's remark, but I don't know if Price was the originator.
Was Wellington perhaps the "fool of the family"? Apparently he wasn't particularly successful in his early life, before, like many younger sons, he joined the army.
Build a man a fire and he's warm for a day. Set a man on fire and he's warm for the rest of his life.
I'll try to find it again (I'm on a tear of his books - doing about 2 a day), but if I recall correctly, "fool of the family" was more generally meant - the officer corps was largely composed of sons who couldn't, or wouldn't, do anything better.
