ABANDONED. YA Sci-fi/fantasy, brother and sister, monkey robot, evil father or uncle?

[Samantha]

I read a book in the early 2000s (it was potentially written around then or in the mid to late 90s) that took place in the future and involved a young girl and her little brother. I believe they lived in a big fancy house with their father or uncle, but then they realized he was part of some evil group, and they escaped. They were accompanied at some point by a (talking?) monkey who either was a robot or had a robot arm. They then went on a big journey and had to stay undercover so their evil father member couldn't catch them.

Unfortunately that is absolutely all I can remember--thanks so much!

[Tab]

Taylor Five ?

Do you remember anything about the cover?
Where did the story take place: Earth, Mars, mythical place, etc?

[Lobstergirl, au gratin]

Samantha, was Tab's suggestion your book?

[Lobstergirl, au gratin]

Lobstergirl wrote: "Samantha, was Tab's suggestion your book?"

No response in 3 years. Moving to Abandoned.