I'm assuming by ageing you mean raising their stats?

If you have two extra kith nests you can get a new kith before leveling up the first one.

The power, guard and speed stats you can get through the minigames, doing hourly quest, cooking food and tailoring things.

The health stat you get by feeding your kith food.
Energy you get by playing with toys.
Reason you can get by reading.

I hope that was helpful :>

thank you :) and yes I meant raising stats XD

also to just add in, if the extra kith nests are in your inventory still, click on them and click the "use this item" feature. Next time you go to the Tatters, you should have the buttons light up to adopt another kith!

(Also, this might be clear already but just in case it's not: there is no way to have more than one active kith at a time, no matter how many kith nests and kith alliances you have. So there will only ever be one at a time displayed on the side bar and pictured with you, and whichever one that is, that is the one who will gain the stat increases from your actions. You can switch between them at any point, of course!)

I do know that, but thank you anyways Sefria!

Yeah... I figured you probably would.... it's just... um. It took me a silly long time to figure out why, when I got a second kith, only the new one was showing at the top of the screen.
>.<
I can be a bit. Um. Oblivious.

oh trust me I am completely oblivious of my actions 90% of the time XD