I think you would be better off waiting until Teddy is at least 18 months old before introducing a new puppy. This will allow Teddy time to mature physically and mentally and will also enable him to be trained to a high standard. My two youngest are only 5 months apart and I found that the eldests training took a few steps back when dallas arrived. I then found myself trying to train two dogs who were at different stages and it was hard work. Vegas was only 7 1/2 months at the time and still had so much to learn......hindsights a great thing :wink: They do get along very well the majority of the time but when they squabble, you will normally find me and Brook hiding in another room
Whatever you decide to do, when the time comes to decide what sex to get, you will need to bear in mind a couple of things. Is Teddy neutered? If he is, then adding a bitch would be no problem but if he is still entire, you will need to make arrangements to keep them seperate when she is in season. This could mean having a family member or friend taking Teddy in or kennelling one of them. Having two entire males can also work but ideally what you want is a puppy whose temperament and personality compliment Teddy's. If Teddy is very confident and bolshy, you would want to get a puppy who was more laid back. The puppy's breeder would be able to help you with this aspect.
I'm sure there will be other members along shortly to give their advise.