According to this answer,
"our seed is as the combined username and password that grants access to our bank account. If anyone obtains our seed, they can login and access our funds."
Despite some existing approaches to generate a safe seed, however consider I generate my seed "manually" that means selecting 81 characters between A to Z and number 9. And someone else also does the same. So, we will have same seed.
Firstly, is it possible such a situation? And if so, what happens?