Adopted two 6-week-old kittens, need help

I've been living with cats and kittens all my life. I've always been told that 6 weeks is when they are ready to be adopted out. I just adopted two baby kitties, they were 6 weeks old. They have been adjusting well. I have an older female cat also, and she has taken to mothering them. But, I was worried because this week they follow her around and try to suckle on her, and cry to her like they are begging for some milk, and my cat will let them attempt to suckle until it hurts her, then she gently gets up and moves. She super sweet to them.
I got on this forum because I worried that 6 weeks really isn't good for the babies and that I should have waited longer to adopt them.
I see that I've been told the wrong information all along.
It's been a week since their mom has nursed them. I imagine her milk is not as available anymore.
The kitties meow when they go potty, like it hurts them. My girl cat licks their bum and cleans them up, And teaches them how to behave.
Do you think they'll be okay?
I feel bad, I sure wouldn't have adopted them that young if I new it wasn't good for them.

The general rule of thumb is minimum of eight weeks to leave mom, and preferably 12. But you've got them now, and it's always good to adopt in pairs so they have a littermate to play with and grow up with. It is especially nice that your older kitty has taken to them so nicely, what with letting them suckle, and grooming and behavior. She is now their substitute mom!

Are they eating wet food or kitten chow? It would be good if you bought a can of powdered KMR (kitten milk replacement) by Petag so they could continue to get the extra nutrition. Mix it and let them drink a dish of it a couple times a day. Or it can be poured over kitten chow, or mixed into their wet food to make a mush.

Are their poops solid? Do you leave a bowl of water so they can drink at will?

Vaccines should not be given before 8 weeks, by the way.

I think your kittens will be fine. But yes, six weeks is young when they are not orphans.

PS: Welcome to the forum!

Thank you for the response! I give them kitten kibble, I put it out for them about 6 times a day or more, and they eat together..so cute. I don't let them graze because my older female kitty (11 years old) would rather eat their food They all have water to drink all day and night.
No, the kitties stools are still solid, soft, but not runny.
I can't tell for sure if they just like to talk when the go potty or if it hurts them. My instinct says it sounds like discomfort.
The 'adopted' mama cat takes cleaning them up very seriously. Paticularly their bums. Hopefully that's helping.
I will get some of that kitty milk to feed them, perhaps that will help.
Is friskies kitten food good for them?

Sometimes they just like to vocalize to let you know they are going potty, or because they are proud if themselves!

I personally prefer Fancy Feast over Friskies. I think that the beef, chicken or fish is the first ingredient (not by-products), and they get superior protein and nutrition. However, that tends to make Fancy Feast a tad bit more expensive, but well worth it in terms of health. Fancy Feast also makes a fish and a poultry kitten wet food, which is easy for kittens to eat and digest. But my kittens, now almost 12 weeks old, refused the kitten version and love the adult tuna feast. Go figure!

Sounds like you have a well-adjusted pair of kittens!