No one will give me dates for the more cheerful Pan Zhang mentioned in this redaction of Passions of the Cut Sleeve Hinsch. Hinsch (reached via google.books) also has the story of Duke Jing of Qi (齐景公) and a lowly official who ogled him, and of Xiang Cheng of Chu and the insinuating Zhuang Xin: but there's no evidence that these men actually had a physical relationship-- though 'promoted him to a position of greatest trust in the royal bath' has a definite ring to it.
I'm assuming Duke Jing of Qi was also a contemporary of Gou Jian and Fu Chai, since his famous prime minister Yanzi (he of the eminently convenient 'to resist desire is not in accordance with the Way' dictum) died in 500BC. ETA- 547-490. But all these examples are from the cultivated north. Zhuang Xin persuades his lord with a story involving Yue boatmen singing suggestive love songs, but I got the feeling from somewhere that he's later. Mind, I can't find any Xiang Cheng of Chu in the king lists, and I wonder if it's an error of Romanization.
Anyway, I'm going to assume my Wu and Yue tribesmen are sweet innocent baa-lambs in this respect, who know that kings of course have favourites but not, you know, favourites like *that*.
Until, but naturally, their civilized Chuite advisors-cum-favourites instruct them otherwise. Possibly with practical examples.