Army was speaking to reporters in Worcester, Massachusetts, two days after DailyMail.com revealed that Kennedy, 22, who is serving 3-5 years for armed robbery, was Herandez's lover.
Army said Hernandez had even written letters to Kennedy's family, who live in Uxbridge, Massachusetts. He produced Hernandez's signature, which he said was written on a letter to Kennedy's step-sister.
He also said Hernandez, who killed himself last Wednesday, had written to his client's businessman-father Matthew Kennedy, using Kennedy's prison nickname 'Pure.'
"Mr. Kennedy, it's Aaron," Hernandez allegedly wrote. "I'm writing to you and Pure doesn't know. I wrote to him just to let him know that I wrote to you out of respect for him.
"He's my brother and he always will be."
The rest of the letter was private, Army said.
The lawyer confirmed DailyMail.com's exclusive that Hernandez had asked to have Kennedy as his roommate in September last year.
"The request, while initially approved, was later terminated by the supervisor of the jail," said Army, managing partner of the Boston law firm Army & Roche.
"The issues as my client understands them was the size difference between Aaron Hernandez and himself.
"The superintendent of the jail informed him that they typically want to house prisoners of the same race and of basically the same size so that if an altercation breaks out there is at least the appearance of equity."
Hernandez was officially listed at 6ft. 2 in. and 245 lb. by the NFL. Kennedy said on his Write A Prisoner page that he is 5ft. 10in. and 175 lb.
Army refused to say whether Kennedy and the one-time New England Patriot tight end were lovers.
"I'm not at liberty to say one way or the other whether or not they were," he said.
Kyle described Aaron as one of the most "powerful forces of a person he's ever known," Army said. "Aaron could take any situation, no matter how bad it seemed, and turn it into a positive. He was always smiling."
Army would not reveal the specifics of the pair's relationship, but said the two knew each other "through correspondence" prior to Kennedy's stint in Shirley, Massachusetts.
But he said Kennedy himself wants to address that himself and will speak publicly about it in the future. "Any discussions relating to that relationship will come directly form his mouth so there is no confusion," he said.
He said Kennedy, who described his sexuality as "straight" on the website Write A Prisoner, which hooks up pen pals for inmates, can't speak now because he has been placed back in solitary confinement on suicide watch just two days after being taken off.
"Unfortunately for my client, suicide watch at this particular institution means he is put into a cell with nobody present - with nothing present - no books, no utensils to write, no television, no radio. He is stripped of all of his clothes and he has a corrections officer who basically sits at the doorway and monitors his every move.
"He has been placed in segregated population, not in his regular cell and he is not able to do the things that he has done over the last 12 months to try to make himself a better person.
"Specifically he has been continuing his education in jail, he has been attending [Narcotics Anonymous] meetings and substance abuse meetings with the mental health counselors.
"Currently all of those services have been suspended."
He said Kennedy was put on suicide watch immediately after Hernandez's death then taken off, but he was put back on after Army had revealed that he was back in the general population.
"Kyle has been taken from his normal group of support staff and friends and isolated. He wants to be put back into the situation he was in before this and doesn't feel he should be placed on suicide watch. He remains in good spirits but is still perplexed as to why that is going on."
Army said Kennedy was "stunned and saddened" by his friend's suicide and when told at 6.30 the morning of Hernandez's death, thought prison guards were playing a joke on him "because they knew of the closeness of their relationship."
Army said that Kennedy, who was jailed in 2015 for robbing a Cumberland Farms store of $189 while wearing a mask and brandishing a "long, butcher-type knife," is convinced that one of the suicide notes that Hernandez wrote was meant for him.
The other two were addressed to Hernandez's fiancée Shayanna Jenkins-Hernandez and their 4-year-old daughter Avielle.
He said he believes the letter did not have a name on it but Kennedy has been told by someone inside the prison that it was meant for him. Hernandez family lawyer Jose Baez insists there was no note left for Kennedy.
"My client was informed by somebody behind the walls of the prison that there was a third letter that was left for him. I do not know who it was. My client did not tell me if it was a guard or an official," said the attorney.
He said parts of the note were written in prison code so outsiders would not be able to understand what was being said.
"We have heard that parts of the letter may be incoherent," said Army. "My client believes that that may be because the letter was written in accordance with language typically used behind the walls of a jail.
"He believes that he could potentially decipher what that letter says. So I am calling on Attorney Baez to release that letter to us."
Army also said that Kennedy has not yet received a $47,000 custom-made watch that Hernandez bought in Las Vegas and promised to him on his 22nd birthday last August.
He showed a picture of Hernandez wearing the watch at an event with his former friends football stars Mike and Maurkice Pouncey.
"The circumstances around that watch were also made known to my client, specifically that the watch was purchased by Aaron in Las Vegas. It was a custom-made watch for him with price tag of $47,000," he said.
Army said Kennedy still believes he is the last person to have seen Hernandez alive inside the Souza-Baranowski Correctional Center in Shirley, Massachusetts. "But because he was removed from the general population he can't 100 per cent sure about that."
Kennedy later issued a statement of his own through his lawyer's spokesman. "I miss my friend Aaron Hernandez," he said. "I'd like to send my condolences to his mother, his fiancée and their daughter."
He then asked the media to respect the privacy of his family. "This is a private matter that doesn't concern them," he said.
Hernandez was serving life without the possibility of parole for the murder of his close friend Odin Lloyd. Five days before his death he had been acquitted of a separate double murder.