My father just passed away and we are three of his children. He had drawn up a will that benefited me to the detriment of my brothers and sisters. The latter are contesting his will. Can they do so?

No. It is perfectly possible to break the equality between heirs. However, the notary will have to ensure that your share does not encroach on the hereditary reserve of your coheirs. If this is the case, they will be entitled to claim, "financial compensation" from you, known as a "reduction indemnity" (art. 924 C. civ.).