Inheritance on Joint Assets


I am looking for some in depth insight on how inheritance on joint assets should be distributed. Speaking to local scholars it is their understanding that in a joint account, 50% of the assets should be distributed as inheritance (in the absence of detailed ownership % allocated). However on the Islamic relief website it states:

“If the husband and wife have joint ownership of an estate, the entire ownership of the asset automatically passes to the surviving partner upon the death of the other.”

Lets say Option 1 is where joint ownership of any assets is considered to be owned 50-50 so that 50% would be distributed as inheritance in the event of a death. It is very common for a couple to build up savings for retirement and maybe even own an house they live in. If 50% would have to be distributed it could put the other spouse in a very difficult position as 50% of their retirement savings would have to be distributed including quite potentially selling the house they live in. Worst case scenario could even include an old widow with no kids.

Option 2 where the joint account is 100% transferred to the survior could have other issues as well where if the survivor marries and dies and new survivor then marries again the money would just get passed along this way without the initially children or family members of the first person who passed away never getting any inheritance. However, there would have to be a decision made by each individual to put money in a joint account or not etc. Which would be similar to an individual giving away all their money while they are alive and have nothing left over for their inheritors.

So taking into how retirement planning currently works and also taking into considerimg potential hardships raised with either option, what is the islamic ruling on joint ownership of assets. Does it transfer 100% to survivor or does 50% need to be distributed as i heritance. Also looking to get insight on what is being practiced currently and how it has been practiced in the past. I.e. if the husband was the sole bread winner of the family and all assets under his name, would assets be distributed and wife gets her share ( 1/8 or 1/4) and she is expected to live off that?

As much detail as possible is appreciated on what the ruling is. Jazakallah.