This is the problem.
The only people who benefit from this sort of conflict are the scumbag lawyers. Everybody else involved losses.
OP, I feel your pain, I am actually in a similar position but am trying to find a resolution that will not involve some bloody lawyer(s) bleeding all the relevant parties dry!
Not wanting to offer advice here, But it would be useful as a first start to see if you can get a letter from your relatives (?) GP on his/her medical opinion as to the relatives (?) legal competance at the time when the, alledged, iffy will was signed.
AIUI, if there is any doubt with older people. The individuals GP is actually supposed to be one of the witnesses for the will to be considered legally valid..