OnePlus 3T - Group Messaging Function?

[AC Question]

Just messing around with my new OnePlus 3T - which I love. But like the last time had an Android (Galaxy S2), I couldn't group message with all my friends who had iPhones. I figured it would better this time around. But whenever I send/receive from multiple contacts, it always up in the thread I have with that person only, including when they write back to me.

My buddy who has an S7 claims that he easily talks to his family on group threads and they have iPhones.

Or do I need to download a 3rd party app? I just want seamless group messaging with my friends who have iPhones.

Thanks!