A man is facing court charged with 50 sexual abuse offences allegedly committed against child relatives over a period of almost 40 years.

The 68-year-old man was arrested at a home on the Central Coast on Monday morning, following extensive police investigations into a report they received in May that a young girl was sexually assaulted by a man known to her.

During their investigation, officers from the state crime command received reports three more children – two girls and a boy – had been sexually assaulted by the man.

A spokeswoman for NSW Police confirmed all four children are relatives of the alleged perpetrator.

After his arrest, the man was taken to Gosford police station and charged with 50 offences relating to the sexual abuse of children – including sexual intercourse without consent, aggravated sexual assault and indecent assault with a victim under the age of 16, sexual intercourse with a child under 10, grooming a child under 14 years for unlawful sexual activity, and inciting a victim under 10 years to commit an indecent act.