I am seeking information on the duties of a son, first born son. Are there any specific laws covering the first born son after a father’s death?

The first born has no specific duties, but is generally expected to be responsible for the arrangements for funeral and family matters. The Halacha considers expenditures by the first born incurred in dealings in family affairs to be shared by the siblings and not to come out of his inheritance. Some explain the law of two portions for the first born to reflect the responsibility he has towards family affairs. There are no special rights accorded to the first born if a sibling challenges his decisions. On the other hand, there is a general principle that one should honor an older brother.