Except for their hair.
You know, I have no idea what went on in utero to result in this kind of coiffure discrepancy.
Maybe it was the TTTS... Owen was all shrink wrapped in his amniotic sac, so maybe his hair was molded to his head due to the lack of extra room. Aidan was floating around willy nilly in all the extra fluid in his sac, so maybe his hair had the opportunity to grow out all mer-man style.
Whatever the case, I feel for Aidan, man. There's no way he's gonna get a date to prom if his hair stays this way.
Look at Owen, he's all suave and sophisticated with the slicked down look...
Aidan, on the other hand, kinda looks like a serial killer.
And even though he's in his jammies, it is not bed head. You can see he has the same unfortunate hairstyle a few days later even in the middle of the day...
Oh well. At least he's got lots of personality.