“Heir-at-law” is usually a specific term defined in state statute. Who qualifies as an “heir-at-law” depends upon the family structure of the individual who has died. In this illustration the father is listed as an heir-at-law. Reference to state statute would be needed to be 100% certain, but parents are not heirs if the deceased left descendants. This reference to the father as an heir would indicate that Andrew Ramsey had no descendants.
Andrew could have had siblings.