Treatment of Undistributed Assets: (As per Inheritance Calculator Guidelines)
There will still be un-distributed amount in some cases, when the deceased does not nominate anyone. This un-distributed amount will be shared among near relatives of deceased i.e., Brother(s)/ Sister(s) in the ratio (2:1)
If there are no Sibling(s) left then Prophet Muhammad suggested by his ijtihad that it will go to nearest male relative.
أَلْحِقُوا الْفَرَائِضَ بِأَهْلِهَا فَمَا بَقِيَ فَهُوَ لأَوْلَى رَجُلٍ ذَكَرٍ
Give the shares to those who are entitled to them, and what remains over goes to the nearest male heir.
(Sahih Muslim no 3929)
People can follow any approach according to this suggestion of the Prophet based on their fiqh preferences.