Neil Patrick Harris' milestone message to twin children after admitting he doesn’t want to know which one is biologically his

Neil Patrick Harris might have been a dad for more than a decade, but he still isn't interested in finding out which of his twins he is the biological father of.

The Albuquerque-born actor, 51, welcomed his kids Gideon and Harper into the world with his husband David Burtka back in October 2010.

The children, who were conceived via surrogate, are now 14 years old and thriving - with Patrick Harris dubbing them 'amazeballs' in a sweet birthday post last year.

The dad marked the milestone by sharing a snap of the teenagers cradling their dogs alongside a poignant message about parenting them both, while acknowledging that they wouldn't even be able to read it.

Let's hope he reiterated his point in their birthday cards then, eh?

In the social media post shared on 13 October, 2024, the How I Met Your Mother star wrote: "Harper and Gideon turn 14 today.

"I have never been more proud of anything in my entire life, and I suspect I never will. My husband David and I marvel at their maturity, are wowed by their warmth, chuffed by their charm.

Patrick Harris pictured with Harper, Gideon and his husband David Burtka (Instagram/@nph)

"We love them both unconditionally, and their hugs fill us with life. We don’t say any of this to them, obvs, or they’d recoil or leverage it to their advantage.

"But they’re not on Insta, so I’m free to speak honestly. They’ll never find out. Happy Birthday, Harper and Gideon. You’re both amazeballs."

A host of social media users then took to the comment section to discuss the teenagers' resemblance to their parents.

One said: "I often wonder how it’s possible that your kids look like both of their dads. Is this a new science thing I’m not aware of? Regardless, they are both beautiful and I wish them the happiest birthday."

Another wrote: "Amazing children and [they] look so much like y'all!"

And a third added: "That boy is your twin. Happy birthday!"

Despite the apparent interest in Gideon and Harper's genetic makeup among fans, Patrick Harris and Burtka, 49, prefer to remain in the dark.

During a 2014 interview with veteran broadcaster Barbara Walters, the Doogie Howser, M.D actor revealed that he had 'no interest' in finding out which twin is his biological child.

The twins turned 14 in October last year (Instagram/@nph)

"I have no interest in [finding out]," Patrick Harris said. "We are their parents and I love them implicitly."

The father-of-two then went on to discuss the intricate process which he and professional chef Burtka had to go through to become dads.

The couple, who began dating in 2004, and got hitched ten years later, used an anonymous egg donor and a surrogate to carry their twins.

Patrick Harris explained: "We inserted one of my sperm and one of David's sperm into two eggs, with the hope that they would both take, just because we both wanted to be dads biologically, and both took, miraculously."

As the children are fraternal twins and not identical, the conception of the twins involved two embryos - one for each twin.

Patrick Harris then admitted that he and Burtka did have suspicions about whose child was whose 'based on their behaviour'.

"It's so funny," he said. "I see myself in each of them at different times."

But he didn’t reveal what those suspicions were, nor who he thought his genetic child was.

The American Horror Story star said that he takes on the role of the 'stern disciplinarian' when parenting Gideon and Harper, laughing: "My voice gets real intense."