Speaking on the courthouse steps on behalf of the family, Aamir's sister, Umbareen Siddiqi, 33, paid tribute to her murdered brother.
"Today's guilty verdict is the right one and as a family we are both delighted and relieved," she said.
"On the 11th of April 2010, a house which was previously filled with love and laughter was brutally destroyed by the callous, vicious attack on our parents and our brother.
"The world has moved on in almost three years since the murder but for us the attack is as fresh as if it happened yesterday."
More top news
Marjorie and Michael Cawdery, both 83, are understood to have been stabbed to death in a killing their family called "incomprehensible".
Detectives have launched a murder investigation following the shooting in Brent, north west London on Friday night.
Hot and humid throughout the Bank Holiday Weekend.