determine a secular lawyerly/philosophical argument that solely upholds the traditional male-female marriage institute's values

Question

I was trying to determine a secular lawyerly/philosophical argument that solely upholds the traditional male-female marriage institute's values. In other words, an argument that could be upheld in a relatively secular and fairly independent court belonging to a nation/country with a relatively healthy democracy.

Therefore, here is my general argument

1)-Let's say that we define marriage as an institute with the Potential for the married spouses to have children as direct bloodline lineal descendants.

2)-Therefore, it would Not make sense in ancient times ( which is probably roughly any time before the 1700s because "first recorded experiment with artificial insemination in humans occurred in the late 1700s, when Scottish-born surgeon John Hunter impregnated a women with her husband's sperm, resulting in a successful pregnancy" Credit Reference: https://www.britannica.com/science/artificial-insemination) to grant a same-sex couple the right to be married because at roughly any time before the early 1700s, there was No way for same-sex couples to have children even if one of the partners in the same-sex couple was willing to some how get pregnant or get an outside surrogate pregnant.

3) If someone disagrees with the argument 1) which was the first argument mentioned then we could possibly counter argue that in ancient times, marriage would need to be defined with the potential to procreate children via naturally reproductive methods( i.e., sexual intercourse) a) because how else would we populate the world with people without engaging in naturally reproductive methods( i.e., sexual intercourse) b) , and furthermore, since the artificial insemination in humans was only successful in the late 1700s then it would Not make sense for same-sex couples to be granted the right to be married because at roughly any time before the early 1700s, there was No way for same-sex couples to have children even if one of the partners in the same-sex couple was willing to some how get pregnant or get an outside surrogate pregnant.

Would the aforementioned arguments be considered valid in a in a relatively secular independent court belonging to a nation/country with a relatively healthy democracy? (Please feel free to suggest improvements that would strengthen my argument)

Answer 1

The main difficulty with this argument is that you would have to establish that marriage is about the production of lineal-bloodline children. That is problematic for a few reasons:

1. It is easily argued that marriage is less a matter of producing children and more a matter of retaining property within certain bloodlines. Note that in the few matrilineal societies that have occurred in the world, marriage is either conspicuously absent or a weak formalization of cohabitation. There is no doubt about maternal bloodlines, so transfer of property via inheritance is non-problematic, and needs no socio-legal frameworks (like marriage) to support it.
2. The question presumes a modern nuclear family structure, which is (historically) exceedingly rare outside of aristocratic and oligarchic classes. In most ancient societies (and many modern ones) child-rearing is a communal affair, with extended families and/or local communities taking part in collective childcare. In such contexts, marriage is more important for easing social frictions that come from sexual tensions — legislating who has the right to sleep with whom, and establishing a systematic procedure for courtship and cohabitation — than it is for maintaining children.

In fact, the entire notion that there is a 'traditional' male-female marriage institution is a bit of a reactionary, ex post facto assertion. We only need to look at a number of powerful ancient societies — Rome, Greece, Persia, etc — in which heterosexual and homosexual relationships stood side-by-side, filling different social functions without any particular problems. The modern prejudice against homosexuality seems to originate from a fairly unique prejudice of ancient Hebrew society against homosexuality, picked up by Christianity as it tried to establish its authoritative roots in Jewish scripture.

So no, your argument would be a hard sell in any rational historical discussion, much less a court of law. This isn't to say you couldn't make a differnent argument from within this particularistic Judea-Christian moral framework, but the argument as given won't hold water.