Killian the husband
I never really believed Killian's words "Well, I've had many a man's wife". I doubt he was celibate, far from it, but as @scripted-downfall wrote in this fantastic post (X), all his words and actions in the scene on the ship served a purpose: defend Milah's honour
"I also think, though: that’s the point. The entire encounter is most assuredly a sham. A test.
Mainly, because this entire encounter is completely and totally out of character for Killian. If there’s one thing that can be said for him, it’s that he is absolutely a man of honor. So, why then does he say, “I’ve had many a man’s wife?” We know for a fact — albeit post-episodically — that he doesn’t make a practice of starting affairs with married women; as mentioned above, when we see him meet Milah in “Devil’s Due,” all it takes for him to back off is for her to say she has a husband"
(and yes I have to put this image, the proof of his honour to women and his start with Milah).
He finally started a relationship with Milah but only after her husband proved a coward a following a code of honour.
My point also with this post: Killian the many men wives man? I would say "Killian Jones, the most faithful ONLY one WIFE ever".
Like he promised to be faithful to Emma's memory forever:
And he was, body and soul
And after reunited he was the most caring, loving, amazing boyfriend and later husband
Because it is just Killian's nature.