Do you know this film where a kid has robot brother who gets pushed into pool at his party and the parents abandon him in forest?

The film you're referring to is "Batteries Not Included" (1987). The robot brother, named XR, is not pushed into the pool at the party, but left there by the adults after he saves Fisby's children from drowning in the pool. The parents don't abandon the brother in a forest, but they plan on taking him and his sister to a different town to keep them separated from the robot XR.