Wanting Sethra to be Vlad's mother or some similar relational situation between our lead protagonists strikes me to be analgous to wanting the two lead characters in a situation comedy to finally "get together" after several seasons of romantic and/or sexual tension. The problem is that "getting together" hardly ever adds anything to the show and nearly always heralds its upcoming death as it turns out that the "tension" was what made the show enjoyable. I don't see any mileage to be gained by having Vlad be related to or have relations with any of his Dragaeran acquaintances, particularly Sethra. Being the carrier of Dolivar's reincarnated soul is already close enough to the bone for such purposes. In light of _Orca_, it might be interesting for Vlad to have a "moment" when he remembers what it felt like to fantasize about "getting together" with Kiera as a teenager, (especially if he discussed this tidbit with Sethra) but given his strong feelings at that age about Dragaerans in general that might never have really happened either.