Hi Andy,
As far as I know the George Younie, Customs Officer, who had the Aberlour property after George Younie, Widower of Margaret McDonald, died was the son of his brother William Younie and Sophia Hay Allerdyce, born in Knockando 24th Dec. 1860. He is NM203766 in the LIBINDX system. He is therefore George snr's nephew rather than his son. As I said, I can find no evidence of any children for George and Margaret McDonald.
Thanks for the contact. Alastair MacDonald