I'm not talking about marriage here... by all means, if you want One, then once you have found One that you hope you could be happy alone with for the rest of your life, then marry them. Marriages in this country and most countries are strictly monogamous.
Really though, you want to marry your soulmate. You believe that there is one person among the 6.8 billion on this planet that your soul is 100% perfectly compatible with. Nearly 7 billion people and you want to find the ONE that is meant for you. Well good fuckin luck. On the other hand, we can look at some numbers. Analyze a bit of probability and chance. Out of 7 billion, lets hope that your soulmate is somewhere around your age group. We wouldnt want one of you to live on for 15 or 20 years after your soulmate dies of old age, right? So lets cut the 7 billion down to 1 billion, and say that what we are left with is your target age group. Unless you're bisexual, you're only going after one gender, so cut the number in half. 500 million remaining. If you're hoping that your soulmate is your ethnicity you should narrow it by at least four fifths or more, so we'll say 100 million left. You're hoping they'll be attractive in your eyes? Lets call it 25 million left. You folks need chemistry and romance? 5 million.
So now you're only looking at your type, the people you would be dating while trying to find The One. Yeah. Right. Only five million people, spread across the entire planet, and you need to find ONE and somehow recognize them as your soulmate. AND hope that they're not already in a committed monogamous relationship, because then you couldnt even date them to get to know them. Sounds like a blast. Really.
So when do you start dating? When do you hope to marry? Lets say you start dating at 15 years old. Dating classmates or something, getting a feel for the dating world. Suppose you have a few relationships through junior high, and then a couple serious ones through highschool, and even throw in a half dozen failed relationships that only lasted a few weeks. By the time you're 18 and finish highschool, we'll say you've had 10 actual relationships. None of those were your soulmate, so keep looking. For every person you date for a year, you might also date 3 for only a week or a month, and spend some time single, so in the years between highschool and turning 21, you date another 5 people. When did you want to get married? When you were 25? What happens if you think you find them, so you spend 4 years dating one person who ... oops ... doesnt think you're the one, and you break up. Looks like your timeline is a bit screwed. You're either out of time, or you have 5 years in order to date the other 4,999,985 people to see if they are perfectly compatible with you.