The other driver may be 100% liable for the damage to your vehicle, but not wearing a seat belt contributed to your injuries, so you are at least partially responsible. File a claim with your insurance company and let them decide which pays what percentage.
It's called 'contributory negligence'; you may possibly have CONTRIBUTED to your own injuries (quite likely did) and therefore are (partially) NEGLIGENT.All states have 'comparative negligence'laws, and all adjusters SHOULD look for mitigating factors, and 'affirmative defenses'. We are looking at "Assumption of Risk" in this scenario. You failed to use your seatbelt, therefore, you ASSUMED part of the risk to your own person, therefore, you were 'COMPARATIVE-ly NEGLIGENT. The adjuster would be correct in offering you only a percentage of your estimated settlement amount.
In the UK - you are entitled to claim compensation, but the amount of compensation you can claim will be reduced by a percentage for "contributory negligence" See the related link entitled "seat belt injury" for a discussion of issues of UK law from wearing and not wearing a seat belt when you are involved in an accident.
The driver of the car.
An adult front seat passenger can be ticketed for not wearing a belt. The driver will be responsible for any minors.
I think it depends on the state, but when...
Interesting. My best guess is that you will be ticketed for the accident, and the driver of the other car will be ticketed for not having the kid strapped in. As far as fault for the kids injuries...
We don't know what state you're in. Some states have laws that say you must have insurance. They will give you a citation and you'll have to pay a fine.