Why the other family disappear when click on person in 4th generation? How to keep the whole tree visible

Answer 1

1. possibly to prevent conguestion

2. set 50 Parents, 50 children, and 50 others and BOOM! your family tree is fully shown, if the fmaily tree is super big (more then 50 gens) then idk.

Answer 2

Try this:  

Click Options  In the fifth column You will see Parents, Children and Others.
Set all three to 50, to see the effect. No "disappearing" family anymore!

In reality you probably want these values to be lower than 50, especially when your tree grows large:
Because e.g. lines between couples can get very long otherwise.

Good luck!