These forums tend to readily swap brood about hives like trading baseball cards. I don't tend to agree with this because it is a good opportunity to spread disease and it induces a great deal of stress that can lend itself to disease and other conditions that can result in hive failure. It also does not provide "true" conditions to evaluate the quality, health, and vitality of the hive on its own.
Focus on Bees -
[...if I could pull a couple of frames of brood out of the two hives to put it in with the packages to give them a boost.]
Why?
The concept here isn't HOW to introduce brood.
It is WHY do you NEED to introduce foreign brood.
Just because you CAN, doesn't mean you SHOULD.
Everything has benefits and costs.
Benefit
-You may gain a growing population or workers and drones several weeks earlier than the package would achieve on its own.
Cost
-You will transfer the varroa in the old brood and give the mites an equal jump start. (maybe even AFB)
Cost
-Brood transfered to the new means less brood for the old. If you are trying to build up a population for a better honey crop, realize at the same time you are also crippling another hive from performing its best.
You need to evaluate the conditions your situation.
(I don't need your answers for the following questions, just please think about them)
Flow/Pollen
Are you in a period of dearth or flow?
Are your other hives readily bringing in pollen?
Varroa
To what degree do your other hives have varroa?
What program are you using to control varroa?
Will the package be in near proximity to the other hives where "drift" needs to be considered?
Foundation
What are you using for foundation?
Are conditions favorable for drawing new foundation?
Would feeding help the current conditions?
Vitality/Robbing
What is the strength of your other hives?
Will pulling frames from old hive compromise their population and possibly their health?
Do you know to reduce the likelihood of robbing?
- reduce the new package (better hive guarding)
- run old hives wide open (more effort/focus to guard home hive(insted of robbing))
Just as you allow a tool to do its work - let your bees work like they know how.
My opinion is that you would be better served to feed your bees and let them pull their own weight.
This opinion would change if:
1. I felt that the new package was absolutely likely to be robbed to death by the two other stronger hives. (When absolutely sure, I would equalize all hives or outyard the package until strong)
2. My other hives were 20 frames solid in brood and I was thinning the brood nest to prevent swarming (even then I just might make up another nuc instead).
Observe your conditions and beekeep appropriately.
Good luck,
JEFF