Punnet Square/genotype question. Hopefully you guys can help me.

I know that if two heterozygous parents have children, that there is a 25% chance that they will have a child that displays the recessive trait.

My question is, do those chances go up as they have more children? For example, a couple has 2 children, and wants to have a 3rd, and the two children don't display the recessive trait, does the chance of the 3rd child having the recessive trait increase to 50% or does it stay at 25%?

Thanks in advance. :)