Future Trunks is a Saiyan-Earthling hybrid and the son of Vegeta and Bulma, both from an alternate future. By the time Present Trunks was born, the timeline had been drastically altered by Future Trunks' and Cell's trips to the past. Therefore, the two Trunks had completely different lives (as opposed to those who lived before the Time Machines arrived, who lived exactly the same lives as their counterparts until the point at which the two timelines diverge, three years before the androids.