Why am I so attached to my one kitty but not as much the other?

Well i just got a 7 week old kitten on sunday. hes everything i wanted for my other kitty who is 11 months, because he (the 7 week old named Oakley) is so playful and so is Bailey (the 11 month old). when I saw Oakley he instantly reminded me of bailey so I got him so Bailey wouldnt be lonely. but I am so attached to Bailey and not really Oakley. I used to have another kitten that was 2 weeks younger than Bailey who I was also really attached to. they were both my babies since i dont have kids yet. but we had to put him to sleep on christmas at 6 months old because he had FIP. I miss him so much! they were inseperable. So is it because I cant replace Baker (the kitty that got put to sleep) with another kitten? Baker will always be in my heart as my little baby! or maybe its because i have only had Oakley since sunday? But i was attached to Bailey and Baker right away..I just miss him so much =(. how can i feel the same about Oakley? I love him and still give him tons of attention but it doesnt feel the same.. =( thanks!