I don't think it was as machiavellian as that. I think they knew what she was from the get go and were not happy at all with anything about her, but were hoping it would run it's course and he'd move on. Unfortunately, as ginger allegedly told some pals he'd "never had sex like it before..." and he was totally hooked on the idea of roast chicken morning noon and night. No doubt panic set in when he said he wanted to marry her and they knew his temper when told no, so william tried to get him to slow down, but here we are. I think the tales of the family welcoming black blood infusion is a load of bollix. There was nothing positive about her. Not that her black blood was a negative or a positive ... it just didn't figure in anything. But when the pair put their heads together they saw it as a great bargaining chip, "We'll tell gangan if she refuses permission we'll pull the race card." so no6 got what he wanted. Again.
I reckon the family just decided Oh for duck sake, he's galloping rapidly toward 40, has no career and is a bleeping millstone round our necks trying to control or pacify him, let smeggy babysit him from now on and we can all breathe easy. Maybe marriage will settle him down. It can't make him any worse, can it?
Well yes, it can and it did.
Sometimes you just need to let them go do their own thang and get it out of their system. Epic fail in this case, but they simply had no choice.
She (and he) was always going to make an issue of race. It was dodged at the wedding when gangan gave them everything they desired within reason, but it was lurking in the wings, the secret weapon smeggy thought would grant them even more goodies from now till eternity. Threats of racism hanging over the family like a Sword of Damocles. But sometimes even grannies dig their little heels in and say no, enough, knock it off, grow up and give my head peace.