Possible situations in further past

[NGUYEN]

Dear Teacher:
Please help me with possible situations in a further past. For the sake of clarity, I would like to number the statements. Please correct my statements if necessary.
The elderly man stood quietly in front of his childhood home, meditating on his relatives:
1. He knew that his parents had passed away. He had only incomplete information about his siblings.
2. His sister might be working somewhere in the same city.
3. His sister might have been working somewhere in the same city.
4. His brother might have perished when the recent earthquake had destroyed the nearby city.
Thank you very much. Respecfully.
Nguyen

[Alan]

All possible.