Yea you will need to use the new twitch api with the ID as Dist mentioned.
But you will need to use multiple call.
You would need to call https://api.twitch.tv/helix/users/follows?from_id=xxxxx&first=100
which returns all the users that the person follows, but not who are strictly live. For the “live” part you need to call to Streams, like so:
IE: https://api.twitch.tv/helix/streams?user_id=User1&user_id=User2&user_id=User3… etc.
You might also have to repeat both of those calls multiple times if the number of follows is > 100, if you do, the second call will need to pass the cursor from the first:
https://api.twitch.tv/helix/users/follows?from_id=xxxxx&first=100&after=CURSORHERE
New twitch api is not super convient for gathering lots of information.
Like if a person has 300 followed, in order to return a full list of everyone live right now you would need to call the Follows api 3 times, then make 3 separate calls to streams in which you fill all the ID’s from the first call into the parameters. Then append the resulting json’s together to get your final list of live users a person follows.
It is a pain.