Probate disagreement

[SNKB14]

Just wondering if anyone has any experience:

DH is one of 3 siblings. Grandmother died 2 years ago now. BIL & SIL do not want to sell property, DH does.
BIL originally said he would buy us out. BIL also talks a load of BS and has made no attempt to follow through with this.
SILs boyfriends parents are now “renting” the property which we did not agree to.
Will states that FIL is executor - he passed away several years ago: Will also states in the event of his passing that the 3 grandchildren should split everything

My question: if my DH applies for probate, do BIL/SIL have reasonable grounds to contest it? Would we likely need a court order to sell?

You may get more help on the Money Saving Expert Forum forums.moneysavingexpert.com/categories/deaths-funerals-probate

I would suggest in your question you state whether or not there was a will, and if so who were the executors. Also relevant is whether your grandmother’s property is in England or Scotland.