I have a broody that has 2 babies 5 weeks old, I also have another hen that just went broody. Would it be okay to put the two them in the same pen and give my new broody some eggs or will they kill each others babies.
Personally, I wouldn't. I had three broodies all with chicks last spring and when two accidentally mixed, they fought with each other like wildcats. In your case, the hen with the five week old chicks is probably getting close to being done with raising them. She'll start to peck them when they come close to her, and that's when you move her back in with the flock and the chicks go into their own grow out pen. If you leave these chicks in the pen with the broody, she might attack them when she comes off the nest with her own young.
I had 2 broody's last year that hatched on the same day they raised there chicks together and all seemed to go well, when one hen lost interest at about 4or5 weeks, the other took over them all, but that is a little different then your situation.