Declan Brady is the son of Brendan and Eileen Brady, and the brother of Paddy and Niamh Brady. Declan arrived to stay with Brendan after being dropped off by Eileen. He later witnessed Brendan attacking Ste Hay, and Ste revealed that he was gay, to which Brendan told him that a man is not a man unless he has a woman and kids. Declan later returned to the flat, and narrowly avoided serial killer Silas Blissett.
Declan later overheard Ste and Rae Wilson discussing Ste's relationship with Brendan, and Declan confronted his father. Brendan was furious, but revealed to Declan that he was also gay and Declan returned home, on good terms with his father.
A few months later, Declan ran away from home, boarding a plane from Ireland to Chester. Declan initially refused to tell him why he had run away, and worried Brendan when he said that he wanted to be respected through fear, like how Brendan gets respect. He revealed that someone had made a homophobic comment about Brendan, so Declan viciously attacked them. When Brendan said that Declan could not stay with him, Declan ran away but Ste found him and convinced him to return home. Brendan told Declan that he was sending him back to Ireland, and Declan left without saying goodbye to his father.
In August 2012, Declan returned and broke into Chez Chez. He told Brendan that he owed people money for drugs back in Ireland, and he could not afford to pay for them. Brendan offered to help him, on the condition that he would stop getting involved with drug dealers and crime.
After the death of his brother, Cam, Simon Walker kidnapped Declan. Cam had suffered severe brain damage from drugs sold to him by Brendan, and Walker planned to kill Declan by overdosing him. Brendan and Ste managed to find the warehouse where Declan was being held captive, but he was unconscious. Declan was rushed to hospital, but made a full recovery and Brendan sent him back to Ireland to prevent him from being in any more danger in Hollyoaks. Brendan later visited Declan in Dublin in December 2012.