The word stepbrother is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 19
Highest Scoring Words With Friends™ Plays In The Letters stepbrother
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Seven Letter Word Alert: (33 words)
betroth, betters, bothers, brother, heptose, herbose, heteros, porters, potherb, pothers, potters, presort, pretest, probers, protest, rebores, reports, reposer, reprobe, reshore, restore, retorts, rhetors, rosette, rotters, sherbet, shorter, soberer, spotter, strophe, tethers, thereto, treetop