My thinking is that this would be a very rare thing. The only way it could happen was if, like with wanda, someone has the prize of a newborn companion, as all other companions are given out by drops. To me, it adds an interesting dynamic - companion breeding would be mega rare so it wouldn't become a mass spam of people breeding their companions, however it would be so interesting to have a companion whose parent is also playable. I'm thinking especially with dragons where there's such a focus on colour hierarchy - there'd be so much plot potential in, for example, a black producing a bronze egg, which could give people amazing plots with their companions. 'My dragon is a higher ranked colour than yours but it is still subservient because yours is its father'.
I really don't see the harm with allowing this just as a variation on 'oops there's another abandoned random egg'. For me at least, having a companion with family would be so much plot potential. And, to again bring up isilme (which I know this isn't but a lot of its lore is taken from isilme) I remember doing a drop where a dragon mother CHOSE to give her egg to an equine for protection c: for cynder it would make IC sense - she knows what an advantage it is to have a dragon bonded to an equine, so she'd want her offspring to be bonded, and would naturally choose a child of Tyra.
[ we are made of greed ]
[ the regime ]