Eldest child is literally a khalid clone

Dominant genes win for a long time so the face and body features should be the only places we see Ilya's genes with some lightening of the children's skin but not as pale.

And yes, this is omegaverse so we do have to throw certain logic out the window. My only gripe with the genre is when there are female-female pairs because their only option is to have girls, genetically speaking.