Reilly is a six-year-old boy who has autism, and his parents have stood by while friend after friend held birthday parties for their children, all without sending Reilly an invitation.
His mum Christine has shared the message her clearly upset husband Shane sent to his friends after one too many parties passed Reilly by.
"Reilly is pretty much non-verbal and is an awesome little boy," Christine told HuffPost UK. "Shane was incredibly upset at the thought of Reilly not being part of his circle of friends. This incident was just the straw that broke the camel's back.
"We struggle for support, we have no regular childcare and feel very isolated."
Shanes message to his friends said, "My so called friends who have kids also have kids parties. Not one invite not f**king one.
"Think about that whilst you go and f**k yourselves; have you any idea how hurtful that is?
"Just for the record in future don't bother, he's not an after thought he's my every f**king thought."
The message found an empathetic audience on Twitter, being retweeted over 1600 times, and favourited more than 4500 times.
The message also received hundreds of replies from people who have been through a similar experience.
"Listen, that's the kind of fire and power you need in a corner when you are in that kind of situation," said one. "Well done dad. Mine is the same!"
"They are not real friends," said another. "He is spot on. We have been through exactly the same."
A third said, "My daughter had a way to handle this. She simply asked the mother of a child with autism what she needed to do to make the party a good experience for him. They had a great party."
Speaking about the massive Twitter response, Christine said, "Inclusion is a big problem for autistic people. Reilly may not speak but he listens and he understands – as he grows I fear for the effects this may have on his mental health, as it does for so many others.
"Every message I have received has the same words. This happened to my son/daughter/granddaughter/grandson too, my child was the only one not invited.
"I would say to other parents in the same position: yes, it's upsetting – no one wants to think of their child as the child that's not invited – but find your own pack. Those who truly understand and run with them.
"Our friends aren't horrible people, I know they feel our struggles. They are mortified that Shane feels this way.
"There's some building bridges to be done now that Shane has spoken about how he truly feels and I think only positivity can come from his outburst.
"The simple advice I give is: just ask.
"Don't assume we don't want to go beause it's difficult, our lives are difficult, often fuelled on three hours sleep. We've often fought a battle before you've stepped into your slippers.
"Ask if Reilly or any other autistic child would like to come even if it's for half an hour but definitely ask.
"Parents know how their children will be in certain surroundings and there is no one better placed to call it.
"The may decline but I can guarantee it will be declined with grateful thanks."
Christine has a blog called "The Life of Reilly" to share insight into what life is like with a child with autism.