cohabitation is where the legal trap gets sprung these days, a marriage contract is not even necessary when de facto relationship has become an implied contract to provide income and share assets.
Males have gradually been relegated to sperm donor status by the perverse incentive structures imposed by court precedents, that is clear ... although I notice they are close to being able to grow ovaries in the lab, last week someone reported they had grown human eggs from stem cells, so the female monopoly on eggs maybe busted and then all bets are off for parentage questions in our esteemed courts.