Custodial parents car insurance will only pay the representative of the estate under the uninsured motorist coverage. If custodial parent files to be the administator, does she have to split the money with the non custodial parent who has never cared for the deceased child or paid on the support order?

I assume the child died without a will. If so, inheritance goes by the laws of inheritance for your area. Note: ANY question of law needs to include your general locale as laws vary by area.