You're right, AG*Gymnast; Jip is Cornelia and Gard's dog; I'd always thought he was the twins' dog more than anyone else's. (But that whole book confuses me a bit; a lot of it seems to come out of the blue to me!)

Anyway, I don't THINK Jip comes up in Nellie's Promise, so I still don't think Jip is hers. But that's just me!