So my nephew is in North Kern state prison my brother died on the 4th of December which is his uncle. Is there any possibility for him to attend the funeral  

This depends on the custody level of the inmate and the decision for him to go is on the warden alone. Your nephew nephew to meet with his counselor and request permission for a family death furlough. The CDCR has this policy statement in their Operations Manual:

A temporary community release log (TCL) shall be maintained in a designated location at all facilities. Custodial escort for a TCL is defined as a Department peace officer properly trained and certified in escort of inmates. Certification requires completion of annual IST classes mandated for peace officer staff on transportation and escort of inmates. Custodial supervision shall be required for inmates who possess any of the following case factors: 
• Designated other than Minimum-B custody. 
• Psychiatric cases documented by the chief psychiatrist as not being a danger to self or others. 
• Housed in AD-SEG for protection only. 
• Has a felony detainer or is serving a concurrent or consecutive county jail sentence, a portion of which must be served upon release from Department custody. 
• Identified with organized crime. 
• Convicted of high notoriety crimes or where presence in a community would likely cause adverse reaction. 
• Designated "R" suffix (restricted custody). Restricted to funeral visit only 
• No parole date or has seven or more years remaining to parole. 
• Inmates in this category shall only be considered for a TCL to attend a funeral of an immediate family member as defined in Section 3000 of the CCR. Unavailability of Escort Staff 
• Unavailability of qualified escort personnel shall be cause to deny a TCL request.