Finlay’s definition of marriage defies logic

He claims it is simply proposed to allow two people to declare their commitment to each other, to end ‘centuries of discrimination’. But, that’s not true either.
Brothers and sisters will still be unable to ‘marry’, nor will people be able to enter in marriages with several partners, no matter how much they all love each other. So discrimination will continue to exist; at least, until the latter groups get their act together to ‘extend the definition of marriage’ further.