The double pregnancies came as a shock to Megan O’Brien, aged 29, and sister, Sara Seyler, age 32, as twins do not run in the family at all.
Now, both women are settling into their new roles as mums-of-two, and the cousins - who were born just 12 weeks apart - are enjoying growing up together.
The odds of a woman having identical twins is roughly 250 to one. A woman whose female sibling has had identical twins becomes twice as likely to do the same, however.
“She held up the ultrasound picture and there were two babies”
Megan O’Brien, aged 29, gave birth to Lilah and Josie, and sister, Sara Seyler, age 32, had Lennon and Parker just three months later.
Talking about the moment she found out Sara was expecting twins as well, Megan said: "My jaw dropped. I got tears in my eyes because there are no twins in our family anywhere. It was so cool that she was having twins too.
"I knew she was having an ultrasound - her very first ultrasound - and then she called me as well.
“I was like, oh, she is probably just FaceTiming me just to tell me how the appointment went, and I answered the FaceTime and she was crying, and I thought ‘oh my god, what’s wrong?’. Then, she held up the ultrasound picture and there were two babies."
The sisters from Pennsylvania, United States, said it was a complete coincidence that they even both fell pregnant around the same time.
Sara, who already had a child before falling pregnant with twins, said: "When I found out I was pregnant, I called Megan, and I was apologising. I was like, I’m so sorry, because I had my first baby, and this was going to be her first pregnancy. “I thought she was going to be mad at me, like, ‘you’re stealing my thunder.’
Megan wasn’t mad at her sister at all, and the sisters said that they loved being pregnant together.
Megan said: "Sara was pregnant before me with her son, but when I was pregnant with twins, you know, I was always three months ahead of her.
"So, she would say, ‘hey, what is going on with you? So, it’s normal, yeah.’ You always had someone to answer questions and kind of relate to, but it was always nice to have her because she just went through a pregnancy and we kind of bounced off each other in different ways."
A large family got even bigger
The sisters said it has been easy to get used to the four new arrivals as they come from a large family, so when they have the whole family around they said the chaos is "pretty normal".
Megan said she has a "really easy pregnancy" but at 32 weeks pregnant she was ready to give birth.
She said: "It was a lot on my body, but the majority of the pregnancy was great and then I hit 32 weeks and I was like, I’m ready.
"Then they ended up coming early because I had high blood pressure. My body was just saying it’s time to come out and then they had 17 days in the neonatal intensive care unit after that - they were very healthy, just had to grow."
Sara said she had a very similar pregnancy to her sister Megan, but her first trimester was "awful" with sickness.
She said: “I was sick. My second trimester was actually really good. I felt pretty good the entire time. Probably around the same time as Megan, like the 30 to 33 week mark, it gets very very painful.
"You know, when you’re carrying twins, you’re basically carrying a full-term baby at like 32 weeks, because you have more than one in there, So, iit gets very, very uncomfortable."
Her daughters were also born prematurely, via caesarean section.
Megan’s daughters, Lilah and Josie were born on November 21 2021 at Doylestown Hospital, Pennsylvania, United States. Lilah was born at 1.33am weighing 4lbs 14oz with Josie being born a minute later at 1.34am weighing 4lbs 6oz.
Sara’s daughters, Lennon and Parker were born on February 8, 2022, at Lehigh Valley Hospital, Pennsylvania. Parker was born at 7.31pm weighing 5lbs 11oz and Lennon was also born a minute later, weighing 4lbs 5oz.
“It was so cool that she was having twins too”
The sisters said it has been an "adjustment" for them both.
Sarah said: "So going from one to three was quite the adjustment. In a way, it was kind of easy, because, you know, I was already in mum mode.
"There’s a lot of days where it is very difficult. I’m a stay-at-home mum right now. So having all three of them some days is a lot. But, it’s lots of fun. There’s more positives than negatives, that’s for sure."
Megan said the adjustment has been a little easier for her as she doesn’t have a toddler to look after to.
She said: "Obviously, I don’t have a toddler in the mix. So, it’s a little easier for me. It’s been great, we’re super blessed - as crazy and wild chaotic it is at times.
"To be a first-time mum of identical twin girls and to share it with my sister, it’s the coolest thing ever."
Megan said it has been "super helpful" that her sister Sara is going through the same experience as her.
She said: "It’s not always rainbows and butterflies. There are some hard days. So, because we have an outlet in each other that has been super helpful.
“It’s a big support for the both of us and then we get to share the funny stories and buy them the same outfit."