can chicks share the brooder

i have 4 chicks that are 2 1/2 weeks old and another 7 due to hatch, once the second lot hatch can they be put in the brooder with the first 4 or will they be picked on by the bigger chicks? i do have another brooder, but would be nice if i only had to have one to deal with. thanks people x x

I don't think this would be a good idea.  The circa 3 week old chicks will be considerably stronger than the newly hatched ones as well as bigger. They may dominate the food and also you should be raising the lamp on 3 week olds so they are off heat by 5 weeks or so which won't suit the newly hatched.
HF