Agressive behavior in dog "sibling"

I have a three year old great dane. He has been a wonderful pet.  My friends around the corner have his brother from the same litter.  Last night while we were at their house for a bon fire he snapped at the neighbors child out of the blue.  I have never seen this dog act like this.  His owner has three children under age 5 and he is wonderful with thiem.  THe dog was just sitting there and his owner was petting him and the child was just standing there also.  Needless to say they are getting rid of the dog.  Do you think that there is a possibility that my dog would turn and react that way?  Could it be in his genes?  My dog has never shown aggression towards anyone--I have two small dogs and he is very gentle with them.  I don't want the dog to hurt anyone.  Thanks

[Aleda M Cheng, D.V.M., C.V.A]

I understand your concern.  No one wants to have a potentially dangerous pet around.  

It sounds as if your dog's brother has social dominance aggression.  Before I can answer your question I have several of my own questions for you as follows:

1. Has your dog's brother ever exhibited any other aggressive episodes no matter how minor prior to this one?  Has your dog?
2.  Are both dogs neutered?
3.  Have the dogs ever been diagnosed with any disease such as Lyme disease, hip dysplasia, elbow problems, or spinal problems?
4.  Have either of the dogs undergone professional training?
5.  Do you have histories of the parents

[peekawho]

I'm sure there must have been warning signs that this dog has issues before this incident.   Is he protective with food or toys?  Was he well socialized?  

Was the child behaving in some unpredictable way?  Sometimes small children jump, play, and run towards dogs in a way that can trigger an unpredictable response.

My Dane is a bit spooky around kids, so I'm extra careful to put him in another room if we have someone over who has a child.  I don't want to take a single chance.

It's heartbreaking that this dog is being given up over this, but hopefully it will be to a home where the owners can provide training, socialization, and the help that he needs without endangering anyone.  As for your dog, if he's never had a problem before with aggression or protectiveness, he shouldn't now.  But with dogs of this size, I would never let my guard completely down.  B/c one bite from a dog this size can be dangerous.  Teach your children dog safety, and remember to always be aware of what can happen and try to prevent an incident from occuring.  

[momfriend]

I looked at the vet's questions, esp has the dog ever had any aggressiveness, and I wonder if this includes behavior as a puppy and when it should end. And of course, if and when you need to make the decision to pass along a beloved pet to a home without kids. WIth a big dog, it seems clear that you cannot tolerate anything like this around kids.

I am trying to figure out if my own puppy only 4 months old, of a stray mother will be a problem to my kids & others since he does bite hard (not just the play biting) when he doesn't like what you want him to do and doesn't respond too well to the response--pin him down till he relaxes a bit & he'll often come back with more snaps, snarls, thrashing & screeches. Otherwise a complete charm & delight, sweet, loving, playful, and always looking happy.