Stewie Griffin: The Untold Story (2005) on Netflix

The major sub-plot circles around the youngest Griffin, Stewie, who has a near-death experience at a pool when a lifeguard chair falls on him, but he survives. After having a vision of being in Hell, he decides to change his ways, but this doesn't last long. While watching television, he and Brian spot a man that looks like Stewie. Brian is convinced that he is Stewie's real father, until Stewie learns that the man is actually himself as an adult, taking a vacation from his own time period. Baby Stewie visits thirty years later to discover that his adult self, going by the name Stu, is a single blue-collar middle-aged virgin working at a Circuit City-type store. Meanwhile, Peter and Lois are trying to teach their two older kids, Meg and Chris, to date. In the future, Chris, who hasn't changed much, is working as a cop and is married to a foul-mouthed hustler named Vanessa. Meg is now called Ron, since she had a sex-change after college.