As soon as you hit your mid 20s, friends and relatives will start asking when you're going to settle down and have kids. You'll probably feel rebellious before really feeling the pressure. If they're asking, then it must be time to settle down and build a family, right?

Not necessarily.

As Sienna Miller shared in a recent interview with Nylon: “Life is really short,” she said. “A lot of what we do is a reaction to what people think you’re supposed to do. ‘Have a kid by 30. Move in, but live together for at least this amount of time.’ All those rules I kind of want to rebel against.”

Of course, nobody wants to be told when to make these major life decisions, especially when they don't feel it at the time. So when is the best time to move in together, marry, or have kids?

The "Best" Time to Move in Together
New studies say that moving in together before marriage won't increase your risk of divorce, as opposed to research in the '90s that suggested that couples who lived together before marriage ended up in less satisfying marriages and were more likely to divorce.

The difference is that the couples studied in the previous data were a lot younger when they got married, meaning they were even younger when they lived together. So it really is about your maturity and not your relationship status, that makes you a better candidate for shacking up before marrying.

According to the National Survey of Family Growth (NFSG) 2006-2010, women aged 25 - 29 were most likely to marry their live-in partners after three years, while women under 24 are least likely to marry live-in partners and most likely break up with them after three years. Also, women who were engaged prior to moving in together or saw cohabitation as a definite step toward marriage were more likely to end up in stable marriages.

The "Best" Time To Get Married
Data from the Pew Research Center suggests that people who get married before they turn 23 are more likely to get divorced. Meanwhile, a 2008 Journal of Political Economy study found that for every year you put off marriage, you face a lower risk of eventually getting divorce. Your level of maturity could be a factor here, but education plays a role too. Putting off marriage until you've gotten your degree makes you less likely to divorce than less-educated couples, according to a 2013 Family Relations study. So maybe marrying later in life may be beneficial after all.

But age aside, couples who date longer before marriage tend to have more satisfying bonds, says a 2006 study published in Dissertation Abstracts International that tracked over 900 people who had been married for three years or more - married couples that dated for less than six months before marriage were the most likely to break up. 

There also may be some great benefits to delaying marriage into your thirties - Single, college-educated women in their thirties earn more per year than women who married before age 30, according to the 2013 report Knot Yet: The Benefits and Costs of Delayed Marriage in America.

So there isn't a magic age number or relationship length that can predict marital bliss.

The "Best" Time To Have Kids
Many newlyweds wait at least a year or so to think about having kids. They want to settle into married life before adding another family member. But interestingly, couples who conceive and have kids before their first anniversaries are more likely to remain married after 15 years than newlyweds who take more time to start a family, according to a 2012 National Center for Health Statistics report.

However, research shows that rushing to have a baby isn't the best option for your relationship or future. The same data set found that couples who got pregnant before marriage were less likely to stay together in the long run.

Then there is the issue of the ticking biological clock. Experts say it's best to have kids by the time you're 35, because your eggs become more fragile as you age, and you won't know whether you'll have trouble conceiving until you try. But the good news is that a recent Human Reproduction study found that 65% of women who started trying to get pregnant at age 40 were successful, so don't assume you need to have a baby before turning 40.