"They're delayed in some ways because of how long they were conjoined, but we're hopeful they'll make up for lost time," says dad Riley Delaney

The Delaney Twins
Credit: Lauren Joy Fleishman

In the past two-and-a-half-years since Erin and Abby Delaney were born conjoined at the head, they’ve been on a roller coaster ride of a lifetime.

After their birth on July 24, 2016 — followed by 10 months of planning, consultations and preliminary surgeries — they were successfully separated after an 11-hour procedure at Children’s Hospital of Philadelphia, making the then 10-month-old twins one of the youngest separations ever.

As parents Heather and Riley Delaney, of Mooresville, North Carolina, look back on their journey in this week’s issue of PEOPLE, Riley, 26, is reminded how “grateful” they are.

“I can’t imagine our lives without them now,” says Heather, 29. “They made our lives complete.”

The surgery was risky on many levels, but the biggest concern was that the girls shared a superior sagittal sinus — the large blood vessel that carries the majority of the blood from the brain.

Delaney Cojoined Twins

“A lot of the time one of the twins who are connected this way dies in surgery,” said lead neurosurgeon Dr. Gregory Heuer. “We easily could have lost them.”

But after two months in the intensive care unit, followed by another two months in inpatient rehabilitation, they finally went home before Thanksgiving in 2017.

To help with the costs that continue to accumulate today, the family created a GoFundMe page that has since raised more than $33,000.

The twins are not out of the woods just yet — and have many more years of therapy ahead — but their parents say they have come far. Three times a week the girls go to sessions to work on improving their motor, speech and eating skills, and once a week a therapist comes to their house.

• For much more on the Delaney family’s story, pick up this week’s issue of PEOPLE, on newsstands Friday.

Erin, who has always been developmentally ahead of Abby, started crawling in July 2018 and will likely walk soon.

Abby, who has yet to crawl, “is so eager to be independent” and “shows such effort,” says Heather.

Even the smallest things, like learning how to eat on their own, is a “huge deal,” she adds.

Delaney Cojoined Twins
Heather, Erin, Abby and Riley Delaney
| Credit: Courtesy Delaney Family

Adds Riley, “They’re delayed in some ways because of how long they were conjoined, but we’re hopeful they’ll make up for lost time.”

Every moment with their girls, who are best friends, makes Heather and Riley more excited for the next.

“They each have their own unique personalities,” says Riley. “It’s so fun to watch them together.”

Erin is “very independent” and “a little attention hog,” says Heather, while Abby is “sassy” and “little miss snuggles.”

She adds: “They’re little fighters and miracles. They have a bright future ahead of them.”