The family of a nine-year-old who was murdered by his grandfather says his death has left a "hole in our hearts".
Stewart Greene, 65, drowned Alex Robinson at his Lincoln home two days before Christmas last year while members of the family went food shopping.
Speaking on the first anniversary of his death, Alex's mother Joanne, father John and grandmother Andrea said their lives changed forever when he was killed.
In a joint statement, they said: "Christmas didn't exist for us last year. We tried to keep it as normal as possible for Alex's little sister Evie, who is now five, but we were all so absolutely shell-shocked and full of grief that it's hard now to even remember what it consisted of.
"This year has been especially hard. Of course last year we had no idea what was going to happen two days before Christmas Day but now we have had the knowledge of the anniversary of Alex's death approaching."
They said Christmas was Alex's favourite time of the year as he loved looking at the Christmas lights.
"He seemed to love the weeks running up to Christmas almost of much as he did the day itself," the family said.
"We would drive around so many different houses as their Christmas decorations went up so Alex could see the lights.
"It was such a lovely thing that we enjoyed doing together and something we will remember for a long time to come."
Alex, who was on the autistic spectrum and did not like having water on his face, was playing on his Xbox when he was left with Greene at the house in Pennell Street.
Greene locked the doors, ran a bath "with both taps to fill the bath even more quickly", walked his grandson into the bathroom and drowned him.
The court heard he then rolled a cigarette and waited for the family to come home.
Sentencing Greene, of Grimoldby, Lincolnshire, to life imprisonment at Lincoln Crown Court in November, Judge Mrs Justice Thirlwall said: "The callousness cannot be overstated."
Alex's father John, 39, said: "I miss my little man so much and life just isn't the same without him. Not only that, but Evie misses her brother and best friend.
"I was so looking forward to him becoming 'double figures' and him growing up to be my little man. Alex was so looking forward to me becoming 40 and found it highly amusing."
Joanne Greene, Alex's mother, said: "My son was a unique and very special young boy. He could be cheeky and mischievous but never with any malice. I am so proud to have had him in my life for as long as I did."