From: Rabbi Moshe Sofer
To: Rabbi Meir Pal
The father's deathbed will was legally invalid due to having only one witness, so the estate belongs to the sons by right of inheritance. The mother's continued residence did not constitute legal seizure of the estate, and her own will has no substantive effect on the inherited property. Sons who do not contest the will may waive the widow's oath on their share, allowing that portion of the kesubah obligation to be distributed per her will, while R' Yechezkel's unconceded portion is added to the general estate and divided equally.
Source: Shu"t Chasam Sofer CM §138