When people first meet 4-year-old Arlo Marlow, they often remark how much the bright-eyed boy looks like his dad, Seth.
They’ll frequently say he resembles Seth’s wife, Leah, too, since they assume she is his biological mom.
But the truth behind Arlo’s origins is a bit more complicated. Arlo was conceived using an egg from Seth, who is transgender. The egg was fertilized with a donor sperm, then carried and birthed by Leah.
“Arlo has two genetic fathers,” Seth tells The Post. “He’s a pretty unique kid.”
The 41-year-old, who transitioned in 2003 at the age of 25, had his transition medically reversed in 2012 so his ovaries would generate enough eggs to create Arlo. Then he immediately switched back to being male.
Meanwhile, as he explains in the new podcast “Pregnantish,” the egg was fertilized with the sperm of an anonymous donor and the resulting embryo was frozen for three years. It was later transferred into Leah’s uterus. The pregnant mom safely delivered 6-pound, 3-ounce Arlo in October 2015.
The baby’s arrival felt like a miracle.
“I thought my transition had cost me my fertility and the path to a family,” says Seth, who told “Pregnantish” that before he started dating Leah, he was convinced he’d stay a “confirmed bachelor.”
“I longed for — but never thought — I would have my own biological child,” adds the technology trainer for a health care company living in Roanoke, Va. “But, as soon as Leah and I got serious and I suggested this course of action, she said: ‘I’m in!’”
Though Seth transitioned to a man and had a double mastectomy, his ovaries remained intact. In order to ovulate again, he merely needed to stop taking testosterone and start a course of estrogen.
“It took quite a psychological toll on me, but I was determined to see it through,” says Seth, whose emotions received a double battering because of an ongoing dispute with his health insurance company regarding coverage.
In the end, the Marlows wound up paying around $30,000 out of pocket for the in vitro fertilization procedure.
As a result of the estrogen, Seth’s body redeveloped curves. After three months, he got a period. In the podcast — available Tuesday — he reveals how he had to sneak tampons into the men’s restrooms at a Chicago airport when he unexpectedly began to menstruate while in transit.
“I’m not a big dude, but I’m a dude with a big beard and a bunch of tattoos,” he laughed. “My trans history only is disclosed if I choose to disclose it.”
Thankfully the egg retrieval went smoothly at a fertility clinic in Syracuse, NY. The couple chose a donor to fertilize the eggs, which were put on ice until Seth and Leah were ready to start their family. Leah had one embryo transferred into her uterus in early 2015. Arlo was born nine months later after a healthy pregnancy.
Even before Arlo could talk, Seth and Leah, 37, also a tech trainer, relayed to him his unconventional beginnings. He has taken the news in stride.
“Recently, we were talking about hopefully adding a little brother or sister to our family and Arlo said, ‘Will we be using your eggs, Daddy?’ ” recalls Seth. “He doesn’t understand the mechanics of the sexual act, but he knows about all the different ways a baby can be created.”
Soon Seth, Leah and Arlo are likely to become a family of four. There are 13 leftover embryos currently frozen in the lab in Syracuse. One will be defrosted and placed in Leah’s uterus within the year.
“It’s a beautiful way to make a family,” Seth says.
For more details, subscribe to the Pregnantish podcast, with new episodes Tuesdays.