inReplyToUserId

@SerializedName(value = "in_reply_to_user_id")
var inReplyToUserId: String? = null

If the represented Tweet is a reply, this field will contain the original Tweet’s author ID. This will not necessarily always be the user directly mentioned in the Tweet.

e.g.

"in_reply_to_user_id": "2244994945"

Use this to determine if this Tweet was in reply to another Tweet.