Musk's daughter, maybe more estranged than his other kids, and Trump's son. The idea is that the "feud" between them could be ended by a marriage of 2 of their children.
Kinda like in Dune where the Bene Gesserit wanted to end the Atreides/Harkonnen feud by marriage and so ordered Jessica to only bear daughters.
Notably, Musk’s daughter is sort of the black sheep of his family; Musk used IVF so he could selectively only have male children, and she is openly trans. She has a significant social media following, largely due to the fact that she has repeatedly put her father on blast. She deserves better.
Because making any decision about an unborn child should be based purely on the medical needs of the child and if applicable the mother. Selecting based on traits is eugenics and I hope I don't need to explain why that is bad. But as I understand the reason Musk is having all these babies is because he totally believes in eugenics, which is terrible.
Edit: just checked, in most of Europe this is very illegal. Gender selection is only allowed if there are strong medical reasons to do so. For example a hereditary disease in the family which only affects one sex and can't be screened for in another way.