Pigeons nest and eggs
Pigeons only ever lay 2 - rarely 1 egg. You must have 2 females lay in the same nest. It will by a huge strain on the parents to raise 4 chicks. You are best to remove 2 eggs. If they are a female only bonded pair then you are best to remove all the eggs as they won't be fertilized.
However, if they are male and female, but another female sneaked her eggs in, that will be OK to leave 2 in there.
I actually had to do this a few times. I raised quails for eggs, and I decided to try eating a pigeon egg. It was delicious!