I am unable to enter into my email id only for alternative email

Hello,
I am unable to enter into my yahoo id.
my friend helped me to open my yahoo id. but 3 year have been passed..i didnt ever try to enter into email ..but now i need my id back.. i lost my sim number which was included on there but my friend add alternative email also ..the problem is i dont know which email he add and i asked him and he also forgot .
I know the password of mine email but the big problem is for alternative email
i am unable to enter ..
help me if anyone can...
urgent help needed.