FINCHforum

So my 7 month year old zebra finch girl laid two eggs with the help of JUST 3 MONTHS ZEBRA FINCH BOY!
More suprising fact that shook me is that they are SIBLINGS.
I think the eggs cannot be hatched due to these reasons; what are your advice for me?

Hens will lay eggs even without a male so there is a chance they are not fertile but I would definetly toss them just to be sure they don't hatch.

They could be fertile, even with the male only 3 months old, so I'd toss them and separate this pair.

If you can't separate them, take out the eggs and replace them with similar-looking fake eggs. (Don't use identical fake eggs, otherwise removing the real eggs would be more difficult.) If you add two fake eggs for every one real one you take out until you reach about 8-10 eggs, they should stop laying, even if they normally would lay more eggs. If you keep removing the eggs and don't replace them, the female will likely continue laying nonstop, which could exhaust her and make her more likely to get ill.
My society finch triplets bred with each other when they were about 5 months old, but after taking out their eggs and replacing them with a bunch of fake ones, both of the females stopped laying. A month later, they still haven't bred and continue to take care of the fake eggs like they are their own.

Horiph

Zebra finches, will begin to mate and lay at amazingly young ages.

The fact that they are siblings will not stop them from breeding . Siblings will mate with each other, as well as parents with their own children, grandchildren, etc.

If you have a nest in there, I would remove it promptly, to discourage further breeding and egg laying. Your girl may still lay an egg here and there, but without a nest, hopefully will not raise any young.

Make sure that your girl has enough sources of cacium available to her (such as cuttle bone, and crushed egg shells).