Jake and Phoebe are brother and sister. Jake is a member of the rroop and it is shown that Phoebe is destined to be a part of the troop when she is older.
Jake is very protective of Phoebe and wontt let anything bad happen to her or lets her be near monsters. It is shown in The Great Punkin, Jake freaks out when Phoebe is trapped in the room with a Ratodon and a Gibbering Troolis, but Phoebe is OK. In Itty Bitty Baby Dragon, Jake wont let Phoebe near her so called Adopted Dragon named Sam, he thinks she will get hurt and he is to dangerous.