Cardiff Crown Court has heard claims that a "lovely, happy beautiful baby" changed in the months leading up to his death.
Finley Thomas from Tonypandy was 17 months old when he died.
His mother's boyfriend, Sean Buckley, has pleaded not guilty to his murder.
Finley Thomas' paternal Great Aunt, Kelly Thomas, told the prosecution that the toddler's appearance changed the summer before he died:
"his appearance, the smell of him, he didn't smell clean like he used to."
When asked if she mentioned this to Finley's Mother, Chloe Thomas, she replied "no".
Cardiff Crown Court also heard that since Christmas 2013, Finley would spend most Sundays with his biological father's family.
When questioned by the prosecution his Great Grandmother, Jennie Thomas, said she noticed a faded bruise on his forehead, but she did not speak to Chloe Thomas about it.
Her husband Alan Thomas also told the jury he "saw the odd bruise".
When Sally Howse QC, who is representing Chloe Thomas, asked whether Finley was behaving normally on his last Sunday visit, his Great Grandmother Jennie Thomas replied "yes, yes he was".
The court also heard from Chloe Thomas' Mother, Carolyn Ann Thomas.
She described Finley as a "normal healthy little boy" and said he had a good bond with his Mother.
25 year old Chloe Thomas from Tonypandy denies cruelty to a young person under 16. Her boyfriend, 28 year old Sean Buckley, also from Tonypandy denies that charge, as well as the charge of Finley's murder.
The case continues .