Thread: True about neuter/spay a MC cat...

I know that question is older and many times people asked before but I'm in troubles with my 2 MC kittens (Baloo and BlueBelle whose are brother and sister) so I re-post the question hoping to have some more suggestions or infos about...
Is true that neuter / spay a MC cat reduce his/her possibility to became bigger? I mean "bigger" as everyone dream that his/her MC will be according with breed standards.
The breeder of my cats suggested me to do that only after one year of age but I would like to avoid the possibility that something will happen between brother and sister during next months...
About fact that Baloo (male) could start to spray around the breeder said me that anyone of her male kittens did that at now (they didn't showed that kind of behavior in the past) and so she is confident that will be the same for Baloo, about time in which BlueBelle will be fertile she said that usually that happen at 10 months of age or later.
What do you think about question? Any suggest for me? An now Baloo is about 4 kg of weight and BlueBelle is lightest, only 2,6 / 2,8 Kg so I guess that Baloo is the cat with mayor possibility to became "bigger"!
Thanks for reading and replies...