61 year old father joined the military after son was killed in action.

This story got me pretty emotional when I came across it today. I’m surprised I've never heard of the Krissoff family who reside about 45 min away from my home town.
Here is an excerpt of their story found in the Huffington Post.

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After learning of his son's death, Bill thought:
"That's what I want to do. I want to be a battalion surgeon."

Bill was as lean as his boys. He stayed fit by biking, hiking, kayaking, and skiing. He figured he could meet the military's physical requirements, so he called up a Navy recruiter in San Francisco and offered up his services. The recruiter posed a series of questions. Finally, he asked how old Bill was.

"Sixty," Bill said.

"Um, that's a problem," the recruiter replied. "You're too old." Anyone over forty-two who wants to join the Navy Reserve medical corps needs an age waiver, the recruiter explained. He wasn't optimistic about the possibility of a sixty-year-old obtaining one.

That August, he and Christine received a voice-mail message from a White House aide inviting them to meet with President George W. Bush after he spoke to an American Legion convention in Reno the following week. They attended the speech with Austin, standing in the back and laughing at the president's self-deprecating humor. As the president was concluding his remarks, they were ushered into a small room with several other families. All of them were "gold star" parents and siblings, those who had lost sons or daughters, brothers or sisters, in Iraq or Afghanistan.

Bush strode in a few minutes later and shook everyone's hand. He spoke at length about the war, explaining his strategy and lauding the sacrifice of his audience's fallen relatives. The Krissoffs listened intently. Iraq was being torn apart by a civil war. U.S. troops were getting attacked daily. Hundreds of Americans had come back in caskets since Nate's final journey home. The war had become deeply unpopular: fewer than four in ten Americans still believed it was worth fighting. When Bush asked for questions or comments, Bill spoke up. He knew what had driven Nate to join the Marines, to find his way to Iraq. He didn't want his son to have died in vain.

"Let's stay the course," he told the president.

Bush approached each family individually and asked if there was anything he could do to help them. Several made small requests for assistance in dealing with death-benefits paperwork. An aide dutifully jotted notes.

Then Bush walked over to the Krissoffs and posed the same question.

"Yes, sir. There is one thing," Bill said. "I want to join the Navy medical corps and serve, but they told me I was too old. No disrespect, but I'm younger than you are."

Bush's eyes widened. He looked at Christine.

"What does Mom think?"

Christine said she and Bill had talked about his desire to serve.

She wasn't thrilled with the prospect of his traveling to a war zone, but she wouldn't stand in the way if going might help her husband heal. "I'm on board with it," she said.

Bush turned to Austin, who had driven up from Camp Pendleton to accompany his parents to the meeting. He was skeptical, but he, too, didn't want to sabotage his father's quest. "He'll be pretty good out there," he told the president.

Bush said he would be meeting with General Peter Pace, the chairman of the Joint Chiefs of Staff, in two days and would mention Krissoff's request. He summoned Karl Rove, one of his top aides, to collect the necessary information from Bill.

"I'll see what I can do," Bush said.

Eighteen months after meeting President Bush, in February 2009, Bill Krissoff arrived in Iraq -- as a lieutenant commander in the Navy -- to spend seven months treating orthopedic injuries at a field hospital on the sprawling al-Taqaddum Air Base near Fallujah, less than ten miles from where Nate had been killed.
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https://www.youtube.com/watch?v=7tyT4glkvBs