death and taxes, certain as

(as) certain as death and taxes

Certain to happen; inevitable and unavoidable. A variation of the proverbial phrase, "Nothing is certain but death and taxes." They just aren't right for each other; they're certain as death and taxes to break up eventually. The two brothers will be forever at each other's throats, as certain as death and taxes.
See also: and, certain, death, taxes

death and taxes, certain as

Also, sure as death and taxes. Bound to occur, inevitable, as in His business is going to fail, certain as death and taxes. This phrase was invented by Benjamin Franklin in a letter (1789) and has been repeated ever since, the government's recurring need for revenue probably assuring its continued popularity.
See also: and, certain, death