Anyone with brothers or sisters has probably experienced a little sibling rivalry. But for the lead characters in the romantic comedy Gray Matters, that kind of jealousy has never been a problem. 

Gray (Heather Graham) and Sam (Tom Cavanagh) are a tightly-knit brother-and-sister pair who've grown up to become the best of friends. But between their jobs and spending their nights hanging out with one another at home, they've hardly had the chance to socialize with anyone else, a situation they want to put a stop to immediately.

In no time, Gray and Sam have a chance encounter in the park with a striking beauty named Charlie (Bridget Moynahan). She catches Sam's eye right off the bat, and he falls so instantly in love with her that he proposes marriage -- which she surprisingly accepts. There's just one little problem: Gray is also in love with Charlie, a dilemma that worsens when the two women briefly but passionately kiss the night before Sam's wedding. Gray understandably freaks out and tries to make sense of these new feelings washing through her, but for her own sake, she has to make the tough decision of whether to ensure her brother's happiness or stay true to her heart.

Gray Matters is the second movie I've seen in the span of a year that takes a lighthearted approach to telling a lesbian love story. The first was Imagine Me & You, which had a predictable structure but also an earnestness about it that boosted its likability as well as my enjoyment of the film. It filled the role of a sweet romantic comedy while developing the main character's realization of her inner feelings. However, Gray doesn't come up to that standard. Writer/director Sue Kramer obviously wants to set a bouncy atmosphere and feature characters often referencing old Hollywood musicals  -- and, on occasion, breaking into random dance numbers. But as admirable as the effort is -- to tell a gay romantic story in a fluffier light than audiences are used to -- Kramer fails to prevent Gray Matters from falling into number of potholes on the road to satisfying viewers.

Even in the crazy, anything goes realm of movie logic, Gray Matters frequently comes across as a hard pill to swallow. Graham and Cavanagh are certainly spirited performers with charm to spare, but the closeness of their characters is difficult to accept and even a little creepy. Also, the personal journey Gray takes after realizing her feelings toward Charlie is a very odd one, populated with the usual prolonged shenanigans indicative of a romantic comedy for a good hour or so, before performing an abrupt about-face and becoming a semi-serious character study in the last act.

In short, Kramer doesn't seem to know how to deal out an even hand with her story, awkwardly slamming the silly and the sincere into one another, resulting in a number of moments that detract from the story. Still,  Graham and Cavanagh deliver satisfactory  performances. And, and despite a hammy turn from Molly Shannon, the supporting cast is solid, especially Sissy Spacek in a brief turn as Gray's psychiatrist and Alan Cumming as a lovestruck cab driver.

In the end, Gray Matters includes more likable parts than it is likable as a whole. If there were any occasion to dust off the old chestnut "close, but no cigar," watching Gray Matters would be it.

MY RATING: ** (out of ****)

(Released by 20th Century Fox and rated "PG-13" for some thematic material, sexual content and language.)