Leaving such a lovely wife alone, and moreover at my sister's wedding with many guests, is reckless. The sense of celebration, alcohol, and temptation would do the trick. The negro noticed the bored girl and was rewarded for his attention and concern for the beautiful stranger. She thanked him like the female the male had chosen for the day. Now her body will remember this unforgettable encounter.
Negroes, mulattoes like to spank white girls in all holes. The fact that this brunette is also a charming girl - gives a glamour to what is going on. And he's just using her as a device to jerk off his dick and lick his balls. He uses it and then he flushes it. And she's satisfied.
Everyone has their own way of persuading to do something, and sex is a very original option. The important thing is that the father was able to talk his daughter into learning, and the contact brought satisfaction to the couple.