Marriage can only be contracted by a man and a woman. A union between two persons of the same sex, call it what you will – civil partnership, civil union – is definitely not marriage.
In any case, if some people want to make use of the word ‘marriage’, then it might as well be called pseudo marriage because that’s what it is, false marriage.
Transexuals, that is men becoming women, are not females but pseudo females. They cannot beget children because giving birth to children is a female prerogative. So a marriage between a man and a transexual likewise is not marriage but pseudo marriage.