That's a very real concern. We have several board members with siblings who have made it work, but also several members who brought home two puppies at the same time and ended up rehoming one of them. So yes, it can be done, but it takes a real commitment and some effort on your part. Having two young children can complicate the process because you may have less time to devote to raising, housebreaking, and training two puppies at the same time.
Generally, if you plan on having more than one dog at a time, the recommendation is to get one, train him/her until they are practically perfect, and THEN think about adding to the family. That can be a year down the road, or it can be 5 years down the road, or somewhere in between. But a GSD puppy is a LOT of work, and I don't know if you're really prepared to deal with two at once. Not everyone is. Mine are half siblings, 11-1/2 months apart in age, and while Dena was a very easy puppy, and already had 4 obedience classes by the time we brought home Keefer, it was still quite a challenge. And we don't have kids, so we were able to devote the time and attention to raising and training them properly.