Neil Patrick Harris remembers 'Doogie Howser' TV dad James Sikking after his death

Neil Patrick Harris is mourning the loss of former co-star James B. Sikking who played his father on the ABC sitcom "Doogie Howser, M.D."

In an Instagram post on Monday, the "How I Met Your Mother" actor shared a headshot of Sikking who died over the weekend, which was confirmed to ABC News by his publicist Cynthia Snyder.

Harris wrote a heartfelt note in the caption of his post, calling Sikking "one of the kindest, wisest, funniest, and most generous people I've ever known."

"A true professional," the caption continued. "He treated everyone with respect, taught me countless lessons, yet always had a spark of mischief in his eyes. It was an absolute honor to be his son. My condolences to his actual family for their loss. #RIP."

Harris and Sikking starred alongside each other as father and son on the show from 1989 to 1993.

The "Hill Street Blues" actor died on Saturday, July 13, at the age of 90 peacefully surrounded by his family at his Los Angeles home, according to a release provided by Snyder which also added that his cause of death was dementia.

Sikking is survived by his second wife Florine, his two children and four grandchildren.

Sikking has also appeared in other TV series including "General Hospital," "Curb Your Enthusiasm," and "Brooklyn South," among others.

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"In a remarkable career Sikking's wonderfully exciting face gave us drama, comedy, tragedy and hilarious farse," the release added. "His career spanned over six decades in television, film and on stage...His talent, integrity and imagination intrigued and delighted audiences."