Faye Johnson, who has stuck by her older brother, said the shamed soccer star would be free to celebrate her son Lucas' birthday with her next year.
The Former England international was jailed for six years in March 2016 for sexually abusing a teenage fan he groomed online.
Johnson, who is currently locked up at HMP Moorland is not due for automatic parole until 2019.
A Prison Service spokeswoman has previously said there is 'no truth' to Miss Johnson's claims.
Wishing her son a happy seventh birthday Miss Johnson tweeted: '7 year (sic) ago the most adorable little boy came into my life! Happy birthday lucas This time next year uncle Adam will be celebrating with us.'
Johnson was jailed for sexual activity with the 15-year-old girl in his Range Rover.
The ex-Man City winger, 30, admitted grooming the girl and one charge of sexual activity with a child, relating to kissing her.
A jury at Bradford Crown Court found him guilty of one more charge of sexual activity with a child. He was cleared of a third sexual activity charge.