You can be dominant and still be the bottom and you can be submissive and still be the top. Or else there'll be no such thing as femdom(yet that's popular with men too). Personality has nothing to do with preference. You shouldn't classify them into categories like 'obey me' or pushiness for seme, or 'taking orders' as uke.
True. I think the pet will be the seme.
Personality isn't really an indicator. In yaoi, the one aggressively pursuing the other is usually the seme. Some authors mix it up, though I just somehow really feel like this isn't going to be that type.
I am going off of yaoi character cliches.
while reading this I could see either of them as the seme. The light haired guy has the obey me and pushiness for a typical Seme, however he also have the naive and 'i'm staight' nature that goes for a tyant uke. The dark haired one has the puppy dog seme quality which is pushy and kinda vauge, also he does do dog play quite well. However he also is very into taking orders and I could see him offering his rear if told to, and he seems secretive and shy about himself. So based on seme and uke of the past I am unsure. what do you think?