His newborn sibling in the film Joshua (2007) was played by his
real-life newborn sibling. The director couldn't find any other young
babies and Jacob's sibling had just been born so his mother was
persuaded to bring her newborn onto the set.
Mother wrote an article for the New Yorker (March 2007) in which she
described her conflicting feelings about being the parent of a child
actor.
He is an accomplished guitar player, and plays guitar in a band with some schoolmates and also plays piano.
His mother, who is American, is from a Jewish family from Russia/Ukraine/Lithuania. His father, who is of Russian-Jewish background, is an immigrant from Moscow, Russia (then in the USSR).
His father (and his father's twin brother) starred in the Russian film
Telegramma (1972) when they were young boys.