You got here ahead of me with a really good post so I'll quote and add my 2 cents rather than doing a full write-up from scratch. My earlier post intentionally focused on the down-side of kids, but there are good things too--I just think the bad parts don't often get a full accounting.

> - You will know everything about them and be responsible for molding them and teaching them and keeping them safe. Taking them from incapable blobs to a person who can think and make decisions and love and hurt.

Helping kids discover the world is really, really cool.

> - You will develop deep relationships and strong feelings for them, more than even for your spouse (which you never thought was possible), and deeper than any other project you'll ever take on.

My Saturday morning outings with my kids (I get coffee, we share breakfast pastry, then we walk around the farmer's market for a while) are my very favorite part of my week. I highlighted that your free time gets sliced to a tiny fraction of what it was when you have kids--far less than half what it once was--but that time with your kids isn't wasted (unless you just hate being around kids and can't get over that, or you can't figure out how to enjoy yourself with kids, I guess). To put it bluntly: you're stuck with 'em, you can mope or you can enjoy yourself, and if you choose the latter it can be a lot of fun. They'll go through rough patches (so, so many) and man will they frustrate you off sometimes even if you have a pretty mellow disposition, but the good times are really great.

> - You will be imbued with purpose whether or not you already had purpose.

I'm definitely more mentally stable with kids than I ever was before. Go figure. YMMV.

> - Start with zero expectations of time. [....] Expect them and learn how to drop things you were doing until the regression is over.

It is vital that you don't try to keep up all the stuff you did pre-kids, or you'll have no time to do any of it well. Some of it you can shift around and squeeze into the cracks or during kid-time, maybe in a different form from pre-kids (PC gamer? Maybe switch to a Gameboy you can suspend at any time and carry anywhere. Runner? Jogging stroller. And so on.), but other things you just gotta let go or you'll be constantly annoyed that you can't seem to get anything done properly, because you're trying to keep up too many things at once. This advice is solid.

> - Be present. Your kids don't have to have the best anything in order to turn out great. They just need you. When you are with them drop everything else even your thoughts. Be there for them. Play with them.

I've gotten in the habit of thinking, in idle times when my kids are awake, "if 80-year-old me were transported back to this moment, what would he do?" Nine times out of ten this drives me to go play with my kids rather than doing whatever time-wasting crap I might have done for that five minutes instead.

> - Take care of yourself and your needs. Make sure you get enough sleep. Your baby is crying and you are desperate for sleep? Check if they are safe, if they have poop, if they've eaten and if they are warm. Done? Get some earplugs and go to bed. Seriously. Take care of yourself!

THIS 10,000x.

> - Any time you are feeling at your wits end reset your assumptions and take care of yourself. Start with what's absolutely necessary and work from there. Feeling stretched financially? Kids don't have to be expensive. You need to feed them. You don't really need anything else, not even diapers. A nearby park maybe.

I highlighted all the ways kids cost tons of money, and oh man do they ever (if you have to you can definitely spend less on e.g. getting into a good school district, but if you've got the means you'll find it hard not to spend that money) but you can easily spend way more than you need to on them. Buy used clothes (Craigslist and swap shop are great for this, so are garage sales), buy used toys--the kids won't mind used things unless you teach them to mind. As mentioned, kids love parks and they're free. Half the crap in the baby section of the store is of little actual use. You don't need to pack like you're making an expedition to an unknown continent when you go out with a baby, with a huge cargo-stroller and/or a huge $300 baby bag (these are real things and many people buy them)--one prepped bottle, 2-3 diapers, and some wipes are all you need 99+% of the time, and often you can get away with leaving some or all of that in the car (if you drive).

(addressing the parent question directly)

> Well, that's all a bit depressing. What would your advice be for me? I'm 26 and my SO wants three children as soon as I'm willing to have them.

I hesitate to advise anyone to have kids or not to have kids. I'd say if you're really set on, say, traveling the world extensively before you're 40... maybe don't. Some stuff's just not happening if you have kids. You cannot have kids and also all the other things you may have wanted. Your retirement savings/debt repayment (say, mortgage) will surely suffer, probably a lot. If you'll consider it a major life failure if you don't retire early and you don't have an incredibly high income (or two), maybe don't have kids. If it's very important to you to at least try to achieve great things in pretty much any field and you don't have enough money to pay for live-in help or an SO who's willing to take on almost all the work of raising the kids (see: the biographies on Wikipedia of people famous for great accomplishments who also had kids) then maybe don't have kids.

Then again, lots of life is making choices about that kind of thing, whether you know it at the time or not. Having kids is a particularly large one with unusually far-reaching consequences, but it's not so different from the rest. If you just really want kids, or of the idea of doing some fraction of the things you might otherwise have done (plus a fair number of things you wouldn't have) but with kids rather than alone or as a couple is very appealing to you, then maybe have kids. Just know what you're choosing to put aside for that, and reach a peace with that fact sooner rather than later to save yourself some painful adjustment and maybe regret. You're doing this rather than that, because it's what you want.