I mean if you don’t love your partner you shouldn’t be in a relationship with your partner, unless that relationship brings other things that convince you to stay with them. If you’re unhappy with your monogamous relationship and want to pursue a non-monogamous relationship, then that’s your decision to leave your current relationship.
Nobody should have to stay with someone they don’t love, and nobody should have to stay in a relationship they are unhappy with. And conversely, everyone should be able to be in a consensual relationship with someone they love, and everyone should be able to be in a consensual relationship that they’re happy with. If your relationship makes you unhappy, you have no personal obligation to stay in it, and if your relationship makes you happy, you have no personal obligation to leave it.
Also you have no obligation to your parents or outsiders at all for that matter. They don’t “deserve” to decide your entire life just because they fucked without protection one day. Don’t let other people control your happiness, especially not cultist nutjobs.
If you want to marry for tax purposes only, there’s nothing wrong with that. Marriage in the current sense is an entirely legal concept, and only exists for legal purposes.
Like I’m sorry if you regret your relationship choice and you’re unhappy with it, that you’re sexually unattracted to your wife and have such strong sexual and/or romantic urges for other people that you want to cheat on her / are so untrusting of your wife that you’re paranoid that she wants to cheat on you, and you felt you’ve gone in too deep to pull out of it, but that’s on you and entirely your problem. Don’t get into a relationship if you know from the start that you’re going to be unhappy with it, and don’t stay in a relationship and waste everyone’s time and emotional effort if it makes you miserable. It’s pretty obvious but I guess some people have a hard time understanding it.