Thanks to mwylie for the contribution to the thread. And to all other contributors.
I found the answer to all this mess late last year when I got the Death Register entry for William Hussey (d. Belfast 1940) from PRONI.
Although the entry was for WILLIAM Hussey, (Labourer), his wife Laura Adelaide Anderson had 3 years later provided documentation to have it revised to Dudley De Vere Hawthorne Hussey, (Ex-Serviceman). Thus proving once and for all that William Jnr. and Dudley were one and the same person.