Raymond Brickett, 65, was charged with gross sexual assault and unlawful sexual contact.
Police said the victim, who is now an adult, told Somerset County sheriff's deputies in December that a family member had assaulted them when they were between the ages of 7 and 14.
Detectives investigating the case said they found information to support the victim's claims regarding the assaults, which allegedly took place between 2002 and 2009.
Brickett was arrested without incident on Jan. 3 and taken to Somerset County Jail. His bail was set at $50,000 cash.
If released on bail, Brickett will not be allowed to have contact with children under the age of 18 or be within 1,000 feet of a school, park or playground.