I had two of these creatures.
Same old story (lovely dogs)
One day the boy got ahold of a Badger and mauled it to death, the display of power was fucking scary. Once my wife pushed out our first kid, I took them both down the vets and they got the needle.
EDIT: adding in a more indepth and important comment below. However, its important to point out regardless of age and health id never ever have a powerful dog in the same house as a newborn baby.
I made the decision to end the life of two older dogs with very little chance of being rehoused. One had bad back legs due to age, the other was brutally violent with other dogs. They lasted well over 10 and had an exceptional life, why on earth would I send the poor things at that age to battersea dog shelter, where there's already pitbulls oozing out of the cages due to the breeds issues.
The decision to put them to sleep was a no brainer, they had no happy life living in a shelter at 11 and 13.