Is "his family" necessary here, please?
"My friend's father left when he was 2 years old".
"My friend's father left his family when he was 2 years old".
Thanks a lot
In BrE, you would certainly be understood if you simply said "My dad left when I was two" or similar. No-one will think you mean that he just popped out to do some shopping (although that might have been his excuse, before never coming back!)
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.