Do away with the puppy playpen thing for awhile until they are a little older and are already trained. The trick is to not give them the opportunity to do bad things. This forces them to do the right thing, then you praise them for it, and it eliminates your inclination to scold them after the fact. Keep them crated when you aren't there, depending on how long you have to be gone. I would recommend going home to let them out and feed them during your lunch break, or get somebody else to do it for you. Consider the size of their bladders being so young, and the fact that they do not have much muscle control in those areas yet. I think crating them separately would be best. Get them two crates and restrict the size of them so that there is just enough room for each to stand, turn around and sleep. If they were litter mates, keeping them together could create behavioral problems which they will learn from each other and both be bad. Keep them separate so that the bad one does not teach the good one bad habits. Let them both learn separately, that way you know which one is the problem and you can train him more intensively in the future. Don't put them together in an open area until they are both reliable. Read as much as you can about this, because there is plenty out there, and everybody's methods differ slightly. You don't necessarily need a book unless you want to get really deep into it. There are tons of websites out there with enough information to get you started on a good routine and explain how to do it, with out getting too deep into why it works.
In a nutshell, here is what to do...
-Crate separately while you are gone, give them just enough room for themselves to sleep.
-Feed on a regimented schedule and keep track of each dog's elimination schedule.
-Don't overly restrict access to water, as this could cause dehydration, digestive problems, etc.
-After learning a little bit of their schedule, try to predict when they will need to go, and take them out before it happens. Also learn their cues so that you can catch them when they may be thinking about it.
-Take them to the same spot every time.
-Once they start learning where the proper place to go is, gradually start increasing the time they have to hold it. Remember though, this must only increase gradually as their physical ability to do so increases.
-The point of all of this is to not give them an opportunity to do wrong. You are forcing them to do the right thing, and then reinforcing by rewarding them when they do it.
-Be careful if they are litter mates. Having two puppies the same age is particularly hard, having sibblings is just asking for torture.
-Be patient, and realize this is not an overnight process. It could take months to get them to a point where they are reliable when you are there, when you aren't there is going to be the tricky part and will take much longer.
One last thing... Avoid animated departures and arrivals. Ignore your pups a few minutes before leaving, and for a few minutes when you return. An animated goodbye will get them excited and then you will be leaving them all alone, thus causing them to be even more upset that you are gone. Then if you get them excited immediately upon your return, they will begin to associate your leaving with a plummeting depression and your arrival with super happy time. It's an emotional rollercoaster for your dog that will lead to separation anxiety problems in the future.
