How to introduce TTRPG's to children?

I am wondering how people introduce TTRPG's to their children. I hope to one day introduce my son to games and was wondering what strategies people have had or done in the past?

At what age did they introduce them to games?
Did they show an interest in your game playing first or did you open it up to them?
Any specific systems designed for a younger audience that you have enjoyed?

My son is still a wee bit young to actually introduce him to a game but it does get me excited at the premise of showing him something I enjoy.

As soon as they can read there is a wealth of games that they can play.
DnD is sorta synonymous with "RPG" in many people's minds so DnD is a good place to start. That way they can easily find others to play with.
On the other hand, you might not want them going out and playing without you, in which case you have the advantage of being a player yourself. Then I would introduce them to the games you like playing, so you can play with them.
If you are a player, the best time to introduce them is when they start showing interest in what you are doing. This may happen well before they can --adequately-- read, or do simple maths, so you might need to find a simple system. There are a few systems designed for kids, an internet search will supply names (I don't want to endorse any of them without having played them more than I have).
I regularly (used to, before these interesting times) run games for teens and down to as young as 11. DnD 5e and Dungeon World have been the standout successes (fantasy is always popular).
I used to run high-school Creative Writing extra-mural classes, and hope to get back to those if the schools ever get themselves sorted out again. Basically PbP with 20-25 players... fun. :)

I introduced my daughter at about age 8 to RPGs, starting with Tiny Horsies (inspired by My Little Pony) and then later with No Thank You Evil. She took to them with enthusiasm and ease.

There are a lot of games with mechanics aimed to engage younger children, including Hero Kids which might be the most popular.

I've heard people strip the mechanics right out and start playing at age 5. Using their toys as miniatures is a great way to get them interested.

When I'm putting my 5 year old to bed, I "DM" a game for her sometimes. I'll give her a premise and ask her to tell me what happens next. Maybe it's a princess pirate captain, and I'll ask what she's doing. "Oh, she's going sailing? What's she looking for? Treasure, of course, a pirate's true prize. Is it on a beach? Oh, well how is she going to get underwater? Hm, good idea, she'll have the air in a box."

It's silly, but it's introducing her to improv storytelling, and building a story with a group. Eventually, I'll introduce her to game rules and dice, but by then she'll be pretty familiar with the general idea.

I used a similar method to skeptical_stun. We started with stories where they decided what they would do or how to react. We also watch and read a ton of fantasy and SciFi stories so the tropes are well-trodden territory.

We played No Thank You Evil last year and now we are playing The Dragon of Ice Spire Peak this summer (they are turning 9 next week).

I've used Fantasy Flight Star Wars/Genesys for as young as 8-years-old. As with anything it depends on the kid/group of kids.

Untold may be a great storytelling intro for younger ages. It's 'powered' by Story cubes. And they have so many varieties of those, any story is possible.

I used to read Norse Myths to my son as a bedtime story, so when the opportunity to learn something in a Fantasy setting came along, it wasn't all that foreign to him.

I think I played my first game with him when he was 8. It was DND but we kept it simple; he didn't bother picking skills, feats, etc. We didn't bother with all the ability scores, just a few; STR, DEX and CON. He played a fighter, because it was simple. He had to rescue the pony that an evil orc had stolen away from a girl with the intention of having it for lunch. The point wasn't to teach him about the rules- that can be tricky and can drain their interest quickly. Instead, we focused on him role-playing and simply "playing pretend". The dice (actually rolling them) were fun and I tried to find reasons for him to have to use them. I isolated what bits he liked and I emphasized those bits.

What's important too, and someone else mentioned this earlier, is to let them SEE you playing, SEE you creating a character, taking notes, rolling dice, building a campaign, etc. Kids like to imitate their parents and if you only play in far away places or behind closed doors, they won't see that and won't feel that curious pull.

Look into Mouse Guard and Pugmire; they're not too bad and very kid friendly; Pugmire probably more.

I guess anything can be kid-friendly if you design it that way, but... this one seems more open to that.

Egads! Mouse Guard is HORRIFIC! Everything is bigger and meaner than you (well, except for the beetles) and everything wants to kill you. :)

There are plenty of 'pastoral' games where adventures are fun and no one gets hurt. Kids like violence though, so they may not be the best fit.

As mentioned, 'simpler', more guided, games can work well with the very young. OSR and WoDu and such --where the basic rules is "because I said so"-- can be a good fit.

I kinda of "lured" my oldest (6) in with minis.

They look like little toys, you move them around on a map, it's perfect to spark interest at that age.

My kid saw me "playing" with them (I was crafting terrain, and kit-bashing minis), they asked what I was doing, I explained, they were interested, and basically begged me for months to play D&D.

They were learning math and so I waited a bit to do it, but eventually came up with a scheme where I reduced D&D to 3 stats (Strength, Speed, Smarts), and just had them describe to me what their character was like and what they had. I gave them bonuses based on that ranging from+1 to +5 in their various stats and using their various gear. They did all the math themself, it was a great way to work on that academic skill while being creative. And just narrated improvised scenarios about them helping a village and stuff. Using the minis on a overland-style map.

They loved it.

I remember my dad being excited about showing me the games Stratego and chess at a young age, and that’s what he grew up with. I didn’t think they were bad, but they didn’t measure up to 8 bit Nintendo. He laughed about how his dad showed him his toys growing up and how boring they were and now I was doing the same to a lesser degree with him.

I experienced the same disinterest from both of my kids with showing them my books, dice, and offering to run a game…despite them liking sci fi, fantasy, and other genres that RPGs tend to follow. It really wasn’t until high school parties that they really showed an interest in getting out my old books and learning more about what some of the games were about.

My take away is that if dad says it’s fun, they see it’s boring. If their friends find it interesting, then it’s cool even if I just got done telling them how much fun the games can be.

They have to find their own way. I’d say introducing them is fine (probably around age 12), and then hope they have nerdy friends.

Dig a lot of the ideas above, and I've had good luck with both Fate (simplified) and Tiny Dungeon with my own kids. I would also point folks towards Quest, which is explicitly aimed at teaching people to play RPGs. It's a great book.

My kids enjoyed board games, one of them was well into the D&D board game Wrath of Ashardalon aged about 4, and they've always liked joining in with Mansions of Madness. I tried them with some child-oriented RPGs when they were a little older, ones with minis like Hero Kids but they never really clicked until they asked about a Harry Potter game and I put a bit of time developing one for Genesys using some existing rules. We've been playing that for about a year now (ages 6-11) and they still seem to enjoy it. I try not to get bogged down in the rules too much but they like chucking a handful of dice now and again. My big mistake was letting them join different houses and they definitely take an antagonistic approach to each other. One of them is big into Avatar so with the new RPG out I might look at one of these Genesys hacks and take some of the fluff from the Kickstarter - I think changing systems at this point would be counter productive.

ETA as of this morning the older one has decided to develop her own investigative RPG based on the set of books 'Murder Most Unladylike' and is currently doing character creation.

So with being blamed for "bumping" my own old thread, I just wanted to share something.

Lately my son (2 1/2 years old) has really exhibited quite the imagination. This morning he randomly pointed to "imaginary bats" he saw and said "Run daddy, we have to get them out of the house". I promptly used this as a game to get him into the car on the way to daycare where he was like "The bats are in the garage daddy, we have to get them into the car with us". He then told our daycare lady all about the bats we saw.

I am starting to think this kid has a great imagination and I hope I can transition this to playing TTRPG's with him in the future.

An Ogre and his Cake is a DM's Guild module meant to be run for children it also has tips for running the module which apply to more than just that module. Clonkers Guide to Being a hero not pay what you want was built with the same intention.
Also Detentions and Dragons is a podcast about running D&D as a teacher (to children)