Why does one try to have their cake, and eat it too? Is sex before marriage eating cake, and is it keeping the cake whole? Yes, you will eat the cake, but you will reap what you are sowing. The cake over time loses its appeal.
There are many who live together, but are not married, and yes they bring forth children, but what are they reaping? They will ultimately reap what they are sowing the cake will disappear too, when judgment comes. No it’s not illegal, it’s not breaking the law, but the partners are ignoring god’s law:
“Let marriage be honorable among all, and the marriage bed be without defilement, for God will judge fornicators and adulterers.” (Hebrews 13:4)