There's no doubting the twin bond.
But for twin sisters in Tennessee, that shared connection is so strong it extended to going into labour at the same time.
In an incredible twist of fate, the sisters Amber Tramontana and Autum Shaw, 33, both, gave birth to baby girls within 90 minutes of one another – on their own birthday.
The sisters even had neighbouring rooms at Fort Sanders Regional Hospital, Knoxville, for the October 29 births.
It's not the first time they've shared a close parenting journey together, with the pair having had their sons, now aged two, just ten weeks apart.
But the coincidence is all the more special for Shaw, who reportedly had difficulty conceiving her second and suffered a miscarriage before falling pregnant with her daughter.
By some serendipitous fluke, the sisters were given the same due date and both went into labour within hours of one another.
Shaw was the first to give birth to her daughter, Charleston Scott, soon joined by Tramontana's baby, Blakely James, according to Good Morning America.
"Autum delivered and we were able to hear a faint cry," Tramontana told the program.
"My husband knocked on the wall as a way of saying congratulations. Ninety minutes later, we deliver and they returned the same knock."
But at Tramontana told local Memphis news network WREG, while they had wanted to have their kids close together, they never expected to have them on the same day.
"We wanted our kids to be able to have that same experience that we had, which is more (like) siblings. And you know, I would say 'you need an Autum and she needs an Amber and you need a person'," Tramontana said.
"That's why we wanted to have babies close together. But we didn't plan that it was going to be this close together!"
According to Shaw, the inseparable pair have shared all their significant milestone moments together.
"From childhood to homecoming to high school to college and nursing school, nurse practitioner school, our sons who are 10 weeks apart, having them close in age and now our girls," Shaw told the network.