One puppy at a time. For multiple reasons... two puppies is a LOT of work (and 7 months is still very much a puppy). The puppies need to bond with YOU, not each other. There are a lot of links on here about getting two puppies, and even though one is older, it all still applies. The general timeline is when the first dog is well trained, issues are dealt with, etc. Two males is iffy not because of an "alpha thing", but GSD's can be same-sex aggressive. It's not as common (and not as scary, usually) with males, but it is a factor to consider. Getting another dog as a playmate for your existing one isn't a good reason, so think about your motives. If you want another dog for YOU, then take the time now to "learn" with the puppy you already have, get him trained and keep up with training, learn the ins and outs.
Plus, two dogs close in age gets expensive and heartbreaking later on.
Edit: Here's the link to the sticky I'd love to get two puppies at once
Like I said, there is an age difference, but the general principles still apply.