"Bob's your uncle" is a British exclamation that means you've achieved something simply. Although its origin is debated, many researchers believe it derives from the nepotism of Lord Salisbury.
“鮑勃是你叔叔”是一句英國(guó)習(xí)語(yǔ)，意為輕而易舉地做成某事。盡管關(guān)于此習(xí)語(yǔ)的起源眾說(shuō)紛紜，但很多研究者認(rèn)為它來(lái)源于索爾茲伯里勛爵的裙帶關(guān)系。

In 1886, Prime Minister Robert Gascoyne-Cecil (Lord Salisbury) surprisingly made Arthur Balfour Chief Secretary of Ireland; Balfour was ‘Bob’s’ favorite nephew.
在1886年，英國(guó)首相?加斯科?塞西爾（索爾茲伯里勛爵）任命亞瑟?貝爾福為愛(ài)爾蘭布政司；而貝爾福是鮑勃最喜愛(ài)的侄子。

There are a few other phrase origin possibilities, but this is the likeliest of the bunch.
也許這句話(huà)還有其它來(lái)源，但這種解釋的可能性最大。