This is gonna get explicit, but here's how Izoten would be born. Taken and modified from DBZ Abridged. All credit goes to TeamFourStar.

KRILLEE: Crazy. So you're like a year older now, huh?



GORUTO: Yeah-huh. Which means he's Teen Goruto now.



GORUTO (TEEN GOHAN AND BORUTO FUSED): Actually, I'm eleven, so that means I'm a pr--



GORUTO: (cuts teen Goruto off) That means you need a birthday party!



KRILLEE: Ooh! Can it be Super Saiyan themed?



GORUTO (TEEN GOHAN AND BORUTO FUSED): *gasps* With little spiky pieces of yellow frosting?



GOKU: (amazed by his son's brilliant idea for a cake) That sounds amazing~! (to Chinata) Chinata! Super Saiyan cake me!

(There is a slight, but dangerous silence...)



CHINATA: Goruto...



GORUTO: Yeah?



CHINATA: Did you take our son into a magical reality outside of space-time for an entire year, bleached his hair without my consent, and suddenly come back home demanding birthday cake?



GORUTO: If it makes you feel any better, it's...not bleach.



CHINATA: It doesn't.



GORUTO: Are you upset?



CHINATA: No...because I know how you're going to pay me back.



GORUTO (TEEN GOHAN AND BORUTO FUSED): Mom, what do you mean?



CHINATA: (opens the front door) Krillee, would you take Goruto (she means teen Gohan and Boruto fused) out for a few hours?



KRILLEE: (quickly) Goruto, we're going to Kame House.



GORUTO: Wait, what does she mean? Guys?



CHINATA: He said one week... (the door slams shut) ...and I'm using it.



GORUTO: Wh-what are you...?

(cut to an outside shot of Goku's house at nighttime, with the sounds of a bed rocking sounds being heard. In short, Chi-Chi is forcibly using Goku for sex as "punishment.")



GOKU: (heard from inside the house moaning as Chi-Chi is heard grunting) RASEN...SHURIKEN...KA... ME... HA... ME... (the bed stops rocking for a few seconds and then a Rasenshuriken Kamehameha wave suddenly bursts through the roof) HAAAAAAAAAAAAAA!