Meg Nagle, a lactation consultant who runs the blog The Milk Meg, shared a selfie of her feeding her sister's son on Tuesday afternoon.
In less than 48 hours the post has been commented on over 300 times and liked by over 3.5k people.
The mother-of-three from Queensland is currently nursing her own 'almost-four-year-old' child once a day and said that she decided to wet-nurse the infant after he refused the bottle.
The Milk Meg posted; 'My gorgeous little nephew! While my sister was at work today I tried to give him a bottle of her expressed milk a few times (which he wouldn't take). I could see he was tired so I popped him on the boob and voila, he was asleep in minutes.'
She has had a mixed reaction, but largely the comment have been supportive of her decision to wet-nurse, which is often seen as controversial.
Adriana Berenice Carbajal said; 'I do not mean this in a harsh way, I am just curious. Does your sister feel ok with this? I have no sisters and I don't know anyone who would do this for me. I am 100% supporter of breastfeeding. I just have never thought of anyone else nursing my son. It's awesome the bond you have.'
Other mums explained that they have been in similar situations, Courtney Chameleon said; 'My sister gave birth to my beautiful nephew nearly 4 years ago now! She was exhausted in hospital and he wasn't quite latching, and she actually asked me "PLEASE! JUST FEED HIM!!!". I felt so honoured to give him his first decent feed and to help my poor sister get some much-needed rest!'
Others, however, have expressed concern. Britney Roybal said; 'I personally get so anxious/angry inside just even thinking about someone else nursing my baby girl. I don't think it's wrong for others if it's something they're comfortable with. I just personally choose to keep my that bond between my baby & myself only.'
And Sofia Clancia said; 'Look I don't want to judge but I really found it disturbing.'