Dog bites from st bernards?

my brother has a st bernard dog that has just suddenly started to miss behave a night, he has been sleeping down stairs with the dog for the past month now while his wife and twin baby boys are upstairs, and things are now getting a lot worse and i'm very worried. the dog started misbehaving only at night by... show more my brother has a st bernard dog that has just suddenly started to miss behave a night, he has been sleeping down stairs with the dog for the past month now while his wife and twin baby boys are upstairs, and things are now getting a lot worse and i'm very worried.
the dog started misbehaving only at night by barging through doors and constantly whinning and the odd bark when the family went top bed, and when he was told to stop it he would growl, then last week he bit my brothers arm but never drew the blood, only on saturday night the same thing happened only this time he bit straight threw my brothers arm and he had to have 9 stitches,they have twin boys that are 9 months old and i,m very worried for them not that the dog has ever shown anyh aggression towards them but i dont think he can be trusted now, my sister-in law feels the same but my brother says he will have him neutered and that will stop the problems they are having.
has any one ever had any experience with st bernard
Update: also the dog randomly ripped a hole in a strangers jacket whilst walking on holiday a year or so ago and he has to be muzzled to go to the vets as he once went for the vet. if any one has had similar problems or has any ideas as to what they could do i would be gratefull as my brother says he cant get rid of the... show more also the dog randomly ripped a hole in a strangers jacket whilst walking on holiday a year or so ago and he has to be muzzled to go to the vets as he once went for the vet.
if any one has had similar problems or has any ideas as to what they could do i would be gratefull as my brother says he cant get rid of the dog but i think it is too risky now but , the dog is fine during the day but at bed time he seems to change.
Update 2: the reason the bite occured is that my brother was trying to stop the dog from charging around the house in the early hours of the morning. the dog has been breed for longer life as well as st bernards only live for around 6 years but the breeder told them they had breed their litter to live for 10 - 12 years... show more the reason the bite occured is that my brother was trying to stop the dog from charging around the house in the early hours of the morning.

the dog has been breed for longer life as well as st bernards only live for around 6 years but the breeder told them they had breed their litter to live for 10 - 12 years don't ask me how as i have no idea.
also the dog has always had the run of down stairs and has had no trainning as such and as he is so unruly they have not been for walks, but the problems seem to be at night.
Update 3: Thanks for all replies, unfortunately my brother has decided to keep the dog but has agreed to try and train him properly and is as i type got a animal behavior expert with him at home.
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