Hi Nikki, my first thought was that this was a misheard MacMillan but that took me nowhere. I then tried Billin,still couldn't find George or Irene but something interesting did turn up.
IGI 1881 Census - 13 Napier St. Heigham Norfolk
MACK Billin 42 Shoemaker
Maria 40
Thomas P 10
Edith 8
Hannah A 4
Laura M 2
All born Norwich
Can't see this Mack anywhere else. I wonder if it was an abbreviation of his middle name which later got added to his surname. Still doesn't find George but could this be his parents and siblings?
Very long shot but as no MacBillins appear to exist before Irene it might be worth looking at.
Val