My father in law passed away suddenly but left a very orderly will & estate (TEXAS). He left everything to his wife of 59 years. Their two sons are married & daughter is a widow with one adult child. What our question is...

Can the eldest son contest the will? Does he legally have the right to receive a share of the estate even when his father's will clearly states that EVERYTHING is left to his mother? So far this hasn't been a problem, however his wife may be pressuring him to do something like this. Also, would the eldest son's wife (daughter in law to the deceased) have any individual rights to contest the will & claim any of the estate? We really need all this money to go to the widow (our mother) for her elder care.

Thank you for any answers/help/suggestions to prevent such occurring.

As long as the will is in order (properly drafted, witnessed, etc) then there should be no problem However, one could contest the validity of the will, and have it thrown out. For example if your FIL was not in his right mind when he signed it, or if there are improper terms in the will, or it wasn't properly signed and witnessed, etc, then it could be contested, and if the will is found to be invalid by the court then the deceased is considered to have died intestate (without a will). If this happens then the estate is divided up among the heirs according to the rules of the state. This can get complicated, given the community property rules in TX, but suffice to say that if this happens some of the property would go to the widow and some would be split up among the 3 children.