Would it matter if the chicks are a couple of weeks apart in age? I cant give you a clear answer. Probably not, especially if they have a reasonable amount of room in the brooder. They are living animals. They dont come with guarantees on behavior or anything else.
Earlier this year I had a broody that was really laidback about her chicks. She let them wander all over, mixing in with the other adults. It just wasnt a problem. The only time an adult pecked at a chick was when that chick became annoying, getting in real close to that hens personal space and staying there. Then a quick peck sent the chick back to Mama. No harm done. Id have pecked that annoying chick too.
Earlier this year I had a chick kill one of its hatchmates, both just under two weeks old. I assume it was the same chick that attacked and tried to kill two other hatchmates at separate times. Mama just watched and did not try to stop it. The first time I saw it attack a chick it injured the chick. I separated the wounded chick overnight then let if back out with Mama and the others. No further problems with it. The next time I saw that chick attack a different sibling, I locked the attacker in isolation overnight. There havent been any further problems but I assure you that attacker is the first that goes in the freezer when they reach proper age. Thats still two months away.
I could give other examples of chicks being attacked or not being attacked. There are no guarantees either way. If it were me trying it, Id make the brooder fairly big and separate it so you can house them side by side for a week or so, then try letting them together. That way the younger are more mobile and they are used to being together. I think youll be OK, but I cant give you any guarantees even if they are exactly the same age.
If you are getting them from separate places, make sure they are not coming from the same hatchery. Otherwise you are defeating your purpose and may as we get them from the same place.