What immortal hand or eye,
Dare frame thy fearful symmetry?
Same mother, different brother?
LOL!
I’ve actually got two (little) cats that I’m sure are ‘brothers from different fathers’ - Superfecundation. ;-)
I think there’s actually been at least one lawsuit over the fact that it’s happened in humans, too...
(My favorite Blake is about seeing ‘a World in a Grain of Sand’...)