In December 2010, EastEnders began broadcasting a storyline in which characters Ronnie Branning and Kat Moon both gave birth in the same episode, but in the following episode, Ronnie 's son, James, dies of sudden infant death syndrome and secretly swaps him with Kat 's son, Tommy .
James Branning, the son of Ronnie Branning and Jack Branning, and Tommy Moon, the son of Kat Moon and Michael Moon , are born on screen on 30 December 2010. In the following episode, Kat is taken to hospital and leaves her father Charlie Slater to look after him. However, Charlie joins a party downstairs in The Queen Victoria Public House . Meanwhile, Ronnie discovers that James has died of sudden infant death syndrome and desperately tries to get help. When she hears Tommy crying, she sneaks into The Queen Victoria and swaps the children. Ronnie soon regrets her actions but by the time she decides to swap them back, James has been found by his step father Alfie Moon and Jack has returned to the country and meets Tommy , thinking he is James. When Kat sees the baby in hospital, she refuses to believe it is Tommy as he looks different, but Alfie convinces her it is because he has died. Alfie comforts Kat by saying he was with Tommy when he died. When a midwife visits Ronnie , she is surprised at how quickly James's club foot appears to have gone. Ronnie is denied access to the funeral by Kat but goes anyway, hiding behind a tree. She later realises she has to put an end to the situation and takes Tommy back to Kat during the wake. Ronnie 's attempts to explain that the baby is Tommy are all misunderstood and Kat demands that the baby be taken away from her.
Ronnie finds out that Michael is Tommy 's real father and tries to keep him away from the baby, especially when he and Jack go into business together. She asks her cousin Phil Mitchell to get rid of Michael but it is not permanent. Michael demands to know why Ronnie dislikes him, and she says he will never understand why, but then lies that it is because he did not support Kat and Alfie . Ronnie tries to tell her sister Roxy Mitchell that James is actually Tommy , and then, unable to cope, leaves Walford. When Jack and Roxy track her down, she says that it is wrong that the baby does not cry. Jack brings her back to Walford, where she continues to care for Tommy but starts behaving erratically. She later returns to the hospital where she gave birth, meets her midwife, Diane McLean, and sees the bed where James lay, and realises she has to give Tommy back to Kat immediately. She tells Jack that the baby is not his son, and then explains to Kat what happened on the night James died. Kat refuses to believe it but takes Tommy , while Ronnie hands herself into the police. Jack says an emotion goodbye the next day as he hands Tommy over to social services. Alfie is interviewed by a social worker, but Kat leaves the hospital unable to cope. However, [[Jean Slater]] tells Kat that it is a miracle that Tommy is alive, so Kat returns to the hospital to be interviewed, and they are reunited with Tommy .