Daga otoko da.

(Yes, that's literally what the caption in the image says.)

Deep Sky and Daiwa Scarlet were both sired by Agnes Tachyon, which basically means they're half-siblings

Rimuru said:

Deep Sky and Daiwa Scarlet were both sired by Agnes Tachyon, which basically means they're half-siblings

Not in the equine world.
Only horses born from the same mares are considered half or full siblings; which is why you'll never see Cygames calling Golshi and DreJour/Orfie siblings but they will call Hayahide and Brian siblings.