Black widow perk output

It does not appear to have an impact on charisma, per se, but according to this site, there is a bonus to persuasion chance, which is broken down as follows:

Persuasion mechanics for this Perk are simple: Rank 1 Black Widow/Lady Killer gives a 10% easier chance to persuade, Rank 2 20%, and Rank 3 a whopping 30% increase to persuade in dialog.

Source: http://www.carls-fallout-4-guide.com/special-stats/charisma/perks/black-widow-lady-killer.php