Hi, this topic has been covered before and everyone has different opinions and experiences. I have two 5 year old EBs, they are siblings and litter mates so have been together since birth. I don't know if that makes a difference or not.
Some members have two males or two females and have had no problems. Some people believe that two females can show jealousy towards each other, and two males can be aggressive to each other. I don't have any experience with having two of the same sex so can't share any experience there. Other people have had good experiences with the same sex with no problems. I think a lot of it depends on the personality of the dogs, and how well the first dog you have has been socialized with other dogs before getting the second dog. Having said that you never know how your dog will react to a new fur sibling, so an introduction of the two dogs should be done in a neutral setting before bringing the second dog into your house to see how they react and interact with each other. A new puppy will most likely adapt with your dog, because he will grow up with your dog, but your dog may or may not accept the new puppy, it all depends on his personality. He could be jealous or aggressive towards the new puppy, or he may totally accept him and they could be best buddies. I hope you find the right fit. Please keep us posted.