"You truly had a spark like no other, Isaac!" he wrote. "Remembering how loved you were and how full of life your time here was gives me great comfort."

The YouTuber finished, "Being your dad was the honor of a lifetime. I’m so proud of you and I love you forever. Rest peacefully, son."

Daniel first shared news of Isaac's cancer diagnosis back in December, which he explained that their family knew was a possibility given that Isaac had been born with Fanconi Anemia, which according to the Cleveland Clinic  is "an inherited condition that happens when certain genes mutate," and can “cause physical differences and blood disorders that lead to bone marrow failure. In addition, it "also increases your risk of cancerous tumors."

At the time, Daniel detailed the link between his cancer diagnosis and Fanconi Anemia.

"We found out last week that Isaac has cancer in his mouth," he wrote on Instagram at the time. "TBH, we always knew this day was coming, as it’s a near certainty w/ Fanconi anemia. But it’s definitely hitting a little earlier than we hoped and is still just such a shocking thing to hear about your child, even if you’ve braced for it for years. Been getting lots of scans and we’re not sure yet how much it’s spread. But for now, the plan is to try and remove the cancer surgically asap."

And he expressed hope that the family could find the right treatment plan for Isaac.

"Our hope is that we’re early enough to cut it all out," Daniel went on. "The location of the cancer will require some pretty extensive surgery and potential bone work, so we’re not sure yet what recovery will look like. But we’re anxious to get it done fast, so surgery will likely be in the next couple of weeks."

He added that they were "taking it a step at a time and addressing the cancer aggressively."

He went on to express gratitude that their family of four had been able to travel to the UK before Isaac's diagnosis, sharing smile-filled photos from their vacation.

"All of this is obviously very heavy on Mindy and I, especially around the holidays," Daniel reflected. "And I’m not sure yet what next year will look like for us. But I am SO grateful that we were able to take an international trip together as a family before it all happened."