If two parties agreed to it under no sense of duress
As long as monogamy is considered the default and something most people wouldn’t ever consider getting away from, it’s impossible to enter a monogamous relationship absent coercion, because the coercion is societal.
Just like there’s no such thing as voluntary employment under a capitalist system, there’s no such thing as voluntary monogamy in a world dominated by Western, Bronze-age sexual politics.
As long as monogamy is considered the default and something most people wouldn’t ever consider getting away from, it’s impossible to enter a monogamous relationship absent coercion, because the coercion is societal.
Just like there’s no such thing as voluntary employment under a capitalist system, there’s no such thing as voluntary monogamy in a world dominated by Western, Bronze-age sexual politics.