Lynks said:
It would probably happen far less frequently. I imagine older vampires would be far more likely to become attached to people from their own time, which means they turned them way back in the day and have been together forever essentially. I imagine an experienced vampire would be far more jaded and less likely to begin a relationship with some human, or if they did the relationship would be extremely one sides with the younger vampire fawning over the elder one and the elder not caring too much. Of course there would be exceptions to this.
From a human perspective - I think you are 100% right. A normal human would eventually become completely dissociated from the mass of mortal humans (explained very well on page 2 of this: http://www.cracked.com/article_17185_7-awesome-super-powers-ruined-by-science_p2.html) i they were immortal.
On the other hand, a vampire, in Warhammer terms, is effectively frozen at the moment of turning - evolving emotionally and mentally at a much slower rate than a normal human. As such they would retain the human outlook they had the moment of their 'birth' for a considerable length of time before becoming disociated from mortal society. Beyond that, they would become cold and quite alien to the human mind. Of course, there will be some vampires who strive to retain their humanity even in these circumstances.
So, I think its all a matter of perspective for the individuial vampire.
And the bloodline, for that matter.
Von Carsteins are bred to be superior and to be the masters of their human cattle. While some will form romantic bonds with humans (such as Vlad and Isabella), it's likely to come from the noble classes when it happens. As such, siring is going to be more politically motivated than romantic, but there will still be a fair share of von Carsteins that do it for love.
Blood Dragons sire other vampires purely from respect of their skill at arms. Love and marriage do not come into it.
Strigoi are quite capable of forming romantic bonds with mortals (the 'Gashnagg, the Black Prince' quotes in NDM and
VC 7th ed show this), but their monstrous nature means that humans are unlikely to be attracted them, making it quite unlikely.
Necrarchs are so completely alien in their mindset that they are unlikely to be capable of love of any kind any more.
And so, to the Lahmians. The Lahmians, more than any other bloodline, have contact with mortal humans on a day to day basis. As such, they are the most likely to form romantic liaisons with humans (and they do, if Genevieve from the novels is anything to go by, as she seems to end up falling for anything that moves). Interestingly, though, they don't tend to turn men as a matter of course (Lesbian Vampire Killers, anyone?)