How does an only child prove there are no other siblings?
Prove to whom? You can't "prove" a negative.
If one of siblings die with mum does the inheritance go to other siblings and the dead sons children or his wife?
Ye, Halle berry has 1 sister.
Being siblings better than only child?
You get more opportunities when your an only child :) my opinion doesn't mean it's a 100 % true
What happens if you had been in an accident and it was considered 5050 because there was no way to prove who was at fault but you had only comprehensive and collision and no liability insurance?
Both insurance companies will pay for their own, depending on your policy coverage.
In NJ if a home is left equally to two siblings and one wants it sold and the other has always lived there does the sibling living in the home have to see or buy it out?
You should mind your own business.