How to manage being partial to siblings in certain situations? How does it effect kids psychology?

It is often v hard to be v partial at least for my case. I have 2 young toddlers and both need attention from me. It can be very damaging for the other child or children if they are scolded or reprimanded without knowing what went wrong and why are they being scolded. To them, we are everything. They are always so eager to please us and doing things that make us happy because they want that attention and love from us. I will always sit them down and tell them that it is wrong to snatch toys or to hit. They need to internalise before punishment sets in.