>>121807764I can think of two ways to do it
>Gwen’s and Ben’s families have always been extremely close to each otherThey’ve know the Tennysons all their lives, to the point where Max is practically their grandpa too and when they heard he’s taking Ben on a cross country road trip they thought "Yeah, why not see if Gwen can join? It’ll get her out of her room and our hair for the summer" The only issue with that is I don’t think it would still make sense for Gwen to hate Ben so much at the beginning of the show so we’d lose that dynamic but I don’t feel like we’d lose that much.
>Gwen is the child of one of Max’s plumber buddies and she goes on the trip because her parents need Max to watch him while they’re away on plumbing businessHer parents need to go on a long business trip to "Amsterdam" to map out a complicated network of "pipes" and it’s "not child friendly environment" so they get Max to watch her because he helped them with a really nasty "clog" in Albuquerque so they trust him with their lives/daughters. This ties Gwen’s family into the whole plumber thing which has it’s own advantages and disadvantages.
Some other anon probably has some better ideas but those are the two I can think up off the top of my head
