It’s a given: boys left to their own devices can come to no good. In the fine MCC Theater production of YEN, a British import, at the Lucille Lortel Theater, the unformed men in question are brothers by the same mother, one static, almost comatose in front of a tv when we meet him, the younger bouncing off walls in paint peeling squalor. Then a wasted mess of a woman comes to visit, as an unseen character barks from a distance, disturbing, and a testament to the power of the drama we create in our imaginations—if we are trusted by good writing, as we are in Anna Jordan’s script. Praise to Lucas Hedges as the taciturn Hench in his theater debut just as he was nominated for a Best Supporting Actor Oscar for his work in Manchester By the Sea, and to his foil Bobbie (Justice Smith). And to the women in this story: Ari Graynor as Maggie, their neglectful mom, dead drunk on first appearance, and Stefania LaVie Owen as Jennifer, a neighboring girl from Wales whose nickname is the play’s title, and wistful hope, as a yen might suggest.