This discussion may contain spoilers!
The Tweedledees (or as I like to call them TweedleDipshits) aren't bad, they're just stupid and greedy. They only work with Bloody Mary and the Crooked Man because they want money. They will get turned on by their bosses and will possibly join Bigby, but only if you didn't kill Tweedledum. I believe they will probably be very useful later on. Even Flycatcher said they weren't bad. I mean they're also pretty stupid as shown by the letters they mailed each other. So they will get betrayed. So in the end I feel they will be very useful, and they're not bad people they've just been put in with the bad people because to them, Bibby's the bad guy, he's stopping them from getting paid.