Pretty good question,
Getting them to grow together on purpose, I think, is what you are asking about. Yes it can be done, but you have to take the approach that you can lose both or more, The only way to accomplish this is by wounding the two plants , and then binding the stalks together. Too young and you kill both.
You would do far better to braid them carefully, or perhaps Bonsai one for a conversation piece. None of my true grafts ever even came close to working, and I know how to graft. Good Luck
smoke in peace
KingKahuuna