Mum's heartbreak: One of these twin toddlers has just months to live

A Brisbane mother who found out one of her twin toddlers has less than 12 months to live is now trying to give him as many life experiences as possible.

Kohan and Chet were born prematurely, weighing less than a kilogram. They were Monoamniotic-Monochorionic twins - identical twins who had shared the same amniotic sac.

But 'Ko' had a long battle ahead of him, born with a severe heart condition and with his organs on the wrong side of his body, mirroring his brother's.

Mum Rachel Irvin has been documenting their journey, throughout surgery after surgery and struggle after struggle, on Facebook.

In October last year, she admitted she was petrified of losing her sick son.

"Scared right through to my soul... As a heart mum you don't know when your time is up with your beautiful child. How do you even process that?" she wrote in a touching post.

For a period, after even more surgeries, it looked as though the tough tot would pull through.

But Ms Irvin's world came crashing down two weeks ago.

"We started with the results from Ko's heart CT scan.. due to the severity of the results found from this scan we have been given 6-12 months left with Ko (as long as he doesn't arrest before)," she said.

"I remember hearing these words and then everything after that is a blur.. I couldn't hear.. I couldn't see.. and I ran out of the meeting as quickly as I could. I could feel my soul crumbling!"

She's now hoping to give her son as many life experiences as possible in the time he has left - including planning "the biggest second birthday anyone has ever seen".

"Every second is going to count until my seconds run out," Ms Irvin said.

She's created a GoFundMe page for her cause, which has already received nearly five times its original goal in less than 10 days.

"As a team we will fight until the last second. So now it's about making 100 years of memories in a short space of time. I want to show Ko all that I possibly can."

They began making their final memories on Friday, after Ms Irvin was able to bring Ko home.