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The pair will join a cast including Sarah Michelle Gellar, who is rumoured to be pregnant with her first child.
The comedy, set in New York, revolves around the dysfunctional lives of three siblings; Alice (Gellar), Mary and Neil.
Orth will play Mary's playwright husband, while Scott, who starred as Palek in Tell Me You Love Me, is cast as Alice's ex, a businessman.
In other pilot news, Diane Farr has been tapped to co-star opposite Peter Krause on NBC's Parenthood, and Andrea Anders is cast as the younger female lead on CBS' comedy Big D.
