Hello again and thanks for using Just Answer.
A party can indeed contest a Will, if they feel it has been prepared fraudulently/or the Testator has been coerced into signing and making the Will by a third party (ie, in the case by the Executors).
However, the onus would be on you to PROVE that this was the case. So, you would have to prove that the deceased did not have full mental capacity at the time the Will was signed and/or they did not appreciate, due to their mental state, the amount of legacies they were leaving to one party or more.
On a side point- When preparing a Will, a Solicitor would always make sure that there was none of the above issues before proceeding, and I would hope that a Will writer would do likewise.
If you do wish to contest the Will, you will need to act quickly and would suggest that you contact a local Solicitor to proceed,
I hope this helps and sets out the legal position.