Were the Houstons of the "Manor of Castlestewart" rather than of the Castle itself ?
John Houston, will c.1698 was of Carnan and Killycolpy, Arboe Parish ? William Houston may have transferred Mullanahoe, Parish of Arboe, to Mr. Cunningham / Conyngham c.1670s when it may have been noted as part of the Manor of Castle Stewart.
Rev. David Houston (rescued at Bothwell Bridge, Scotland)may have been in Arboe Parish.