A source close to the family confirmed the sad news about the 47-year-old's cause of death, to People magazine.
Speaking of the transgender actress, they explained that she "had been suffering for a long time. She was sick for years."
"At one point, she wasn't able to leave the house; she was in bad shape."
During Alexis' final hours, the insider told the publication that "the whole family rallied around her. And in the end they were always there to support her. Everyone knew [her death] was imminent. It was a matter of time."
Find out more on the beloved actress in the video below! Article continues...
As for the Arquette family, the insider admitted they're "doing as well as can be expected. They all love Alexis very much."
Her untimely passing was announced by her brother Richmond on Facebook.
Richmond’s announcement read, "Our brother Robert, who became our brother Alexis, who became our sister Alexis, who became our brother Alexis, passed this morning September 11, at 12:32 am.
"He was surrounded by all of his brothers and sisters, one of his nieces and several other loved ones. We were playing music for him and he passed during David Bowie's Starman," he penned.
On Sunday, the family released a touching statement about their departed loved one.
"Alexis was a brilliant artist and painter, a singer, an entertainer and an actor."
The statement continued that Alexis's "career was cut short, not by her passing, but by her decision to live her truth and her life as a transgender woman. Despite the fact that there are few parts for trans actors, she refused to play roles that were demeaning or stereotypical. She was a vanguard in the fight for understanding and acceptance for all trans people."
The family spoke of the actress, taking pride in her work and her activism.
"She fiercely lived her reality in a world where it is dangerous to be a trans person – a world largely unready to accept differences among human beings, and where there is still the ugliness of violence and hostility towards people that we may not understand. ... "
"We learned what real bravery is through watching her journey of living as a trans woman. We came to discover the one truth – that love is everything."
Alexis, born Robert Arquette, was part of the Arquette family dynasty of actors including Patricia Arquette, David Arquette and Rosanna Arquette.
The actress was best known for her role as a Boy George impersonator in The Wedding Singer.
Following the tragic news, her brother David Arquette headed to Twitter where he spoke of his pride and love for his sibling.
"Thank you all for your love and kind words about Alexis," he shared on social media. "My hero for eternity."