That’s no law, that’s just the definition. Laws concerning incest differ from country to country but afaik they usually involve penis in vagina penetration (because of, frankly, outdated definitions of “sex”) so twin sisters could go at it if they like.
Comment on Anon has a very specific goal
IronBird@lemmy.world 4 hours agosounds like an outdated law tbh, incest bad cause it leads to incest babies. no chance of procreation no incest baby
Lumidaub@feddit.org 4 hours ago
DrivebyHaiku@lemmy.ca 3 hours ago
Well incest bad also because it tends to ruin families regardless of gender. Most of the time it resolves around an older sibling taking advantage of a younger child and has the power dynamics of any other type of pedophillia
Even when it’s equitable and between adults people’s psychology treats sexual partners differently. Introducing sexual relationship dynamics : potential jealouslies, the desire of siblings to grow apart and the secrecy pressures of keeping their relationship secret can up the risks of siblings hating each other.