Neil Smith is the son of Neil Smith ,Vanessa Jenkins, nicknamed Smithy and Nessa. When their best friends' Gavin and Stacey meet in London, Smithy and Nessa do not get along at first but end up sleeping together in a hotel. Following this they refuse to speak about the "mistake", but have sex while visiting Gavin's parents Pam and Mick. This when baby Neil is concieved. A few episodes later, at Gavin and Stacey's wedding, Nessa reveals to Stacey that she is pregnant but does not tell Smithy until the beginning of the next series, when Gavin and Stacey return from their honeymoon. An upset Smithy disappears for a few hours before being tracked down by Gavin, Mick and Bryn, Stacey's uncle. Nessa and Smithy continue to have an awkward relationship, ending once with Smithy's proposal to Nessa, which is laughed off by the family.
Nessa continues to get larger and larger, now staying at Stacey's mum Gwen's house. In the final episode of Series Two, Nessa goes into early labour while Stacey is down in Essex with Gavin, Pam and Mick. She is looked after by Gwen, Bryn and her partner Dave Coaches. In Essex, Gavin and Smithy's sister Rudi look for Smithy before finally finding him in the Rose and Crown. Nessa is taken to the hospital where her labour pains continue and Stacey arrives with Pam and Mick who have come down before Gavin and Smithy. The duo hurry towards Barry, encountering several setbacks including not having enough money for the bridge and being stopped by an over-friendly police officer. They arrive just after Nessa gives birth to baby Neil, and Smithy is emotionally touched. They name him after Smithy and Nessa's father. The birth also leads to the reunion of Gavin and Stacey, who have been having marital problems.
Baby Neil makes cameo appearances throughout Series 3, with Smithy often arguing with Nessa's partner, Dave, who she has become engaged to, over who looks after the baby better. He does not make his next important appearance until the last episode of Series 3, where Nessa is planning to marry Dave. Smithy looks after Neil for her while she gets married, but decides that he does not want her to marry Dave and heads to Barry with baby Neil. He subsequently bursts into the wedding, and tells her that she should not marry Dave because she has him to support her. She decides to do as he says and thanks Dave, before leaving. This is baby Neil's last appearance.