In the finale, Doyle lays three flowers on Van Rook's grave...then picks one of them up and says "two is plenty". This echoed the "lesson" that the notorious cheapskate Van Rook was teaching Doyle back in the very first episode; Doyle knew Van Rook would've wanted it that way.
While the love Doc and Drew have for Zak is cute enough, the fact that they love the cryptids just as much is adorable. Drew's willing to carry a fully grown Komodo Dragon through the snow on her back, the entire family braves Weird World to save Fisk, and they constantly refer to the trio as "their boys". The Saturdays don't have one son. They have three.