(a) Subject to subdivision (b), evidence of a statement by a declarant who is unavailable as a witness concerning his own birth, marriage, divorce, a parent and child relationship, relationship by blood or marriage, race, ancestry, or other similar fact of his family history is not made inadmissible by the hearsay rule, even though the declarant had no means of acquiring personal knowledge of the matter declared.
(b) Evidence of a statement is inadmissible under this section if the statement was made under circumstances such as to indicate its lack of trustworthiness.