The mum of two-year-old Dylan told Northampton Crown Court her son would always cry after staying with his father, the man now accused of murdering the toddler.
Northampton Crown Court heard Dylan's mum say he always "clung to her" whenever he returned back home and that Kennedy would also tell Dylan "to stop acting like a little girl" whenever the toddler cried.
Giving evidence from behind a screen, she told the court: "I am Dylan's mother.
"When I was 16 I met Mr Kennedy and we had a brief sexual relationship - which I became pregnant from.
"After that I had no contact with Mr Kennedy until late September 2017.
"Dylan was born at 34 weeks, premature, but he was well looked after and grew up to be a normal healthy boy.
"In December 2016, Dylan took his first steps - he had begun to get his first teeth at just over one-year-old.
"There was a time when Mr Kennedy wanted to know if he was Dylan's father. A DNA test in September 2017 confirmed that Mr Kennedy was Dylan's father.
"It was agreed that he could see Dylan for a short period of time initially.
"On November 25, Dylan stayed at Mr Kennedy's, this was after Dylan was taken for a GP appointment on November 23 for a chesty cough.
"Between the 11th and 15th December, Dylan stayed with his father.
"When Dylan came home from his father's he would look at me and cry and say 'mummy' and cling close to me.
"But he always seemed fine. His dad would say 'stop acting like a little girl' when he saw Dylan cry.
"Dylan was quite insecure, when he would play and if I had walked out of the room he would follow me. He didn't even want to stay with my mum or dad, he just wanted me. If someone else was pushing his buggy other than me - he would cry.
"At first he was unsure, but then he would soon interact with his father - he wouldn't be scared of Mr Kennedy.
"I would get sent Snapchat videos of Dylan from his father - when he couldn't understand what Dylan was saying. This was at the start but after a while it got better.
"Dylan knew how to say please and thank you, his mum and dad's names. If he was hurting he would be to tell you by saying 'hurt, hurt'."
The court heard Kennedy sent Dylan's mother a text message on December 14 to tell her Dylan was "really poorly" and wanted to return home.
She added: "I was told that Dylan was dancing on the coffee table, slipped and banged his head and was sent a picture of the injury by Mr Kennedy. I didn't see any other injuries.
"At 11.23am on December 15, I was Snapchatted by Mr Kennedy. The message said that he was getting Dylan ready to take him to town because he had to sign on.
"In the image Dylan was sitting on the bed and wearing his pyjamas. I messaged him back that it was fine.
"I had been called by Mr Kennedy which lasted one minute and 36 seconds, and he said Dylan was walking behind him and had slipped over on ice and hit his head.
"He had taken Dylan back to the flat and said he was going to give him a cup of orange juice to give him some energy.
"I was under the impression I was on speaker phone. I said Dylan, it's mummy, are you ok? "There was no response. I kept saying Dylan's name.
"At 12.06pm, I told my mum about Dylan and she said to message Mr Kennedy - he messaged me back saying he was ok and was just sleeping. I was reassured by that message.
"At 12.43pm, he told me Dylan had stopped breathing and he had called an ambulance and for me to head to the hospital. I phoned my mum and cried.
"He then phoned me again later to say that Dylan had died. I never knew Mr Kennedy was involved in the drugs world.
"If I knew there were drugs in the flat I would never have allowed him to stay at Mr Kennedy's flat."
The trial will resume tomorrow (Thursday).