Complex sentence: Martin and writer & editor Sarina Rowell, in 2013, began writing a new sitcom "Childproof" about a young couple who decide not to have children but after four years were unable to sell the idea to any of the TV networks.
Split into simpler sentences: Martin and writer & editor Sarina Rowell, in 2013, began writing a new sitcom "Childproof" about a young couple who decide not to have children. But after four years, Martin and Rowell were unable to sell the concept to any of the TV networks.