Is the small one the male

[Zydan777]

I am assuming based on the twitching he does around the other larger black clown fish he is the male here is a video of him twitching the the other one swims up to it

 

[W1ngz]

Yes, that's generally how it goes, the largest more dominant is the female, the smaller is the male and will put itself into submissive postures (belly towards her) and do all kinds of 'sexy time' twitches.