There's a deep connection between Kristen Wiig and Bill Hader, but it's not quite a sibling relationship. For nine years they were part of the ever-growing Saturday Night Live comedy troupe, which also included Tina Fey, Amy Poehler, Will Ferrell and Maya Rudolph during their comedic tenure.

It's no wonder then that so many of them appear in each other's films, like some form of professional incest.

Wiig and Hader have appeared on the big screen before, most noticably in 2009's hugely enjoyable Adventureland, but this is the first time they've taken their relationship to a whole new level: as twins.

Siblings often go their own way, but it's been ten years since Maggie (Wiig) and Milo (Hader) have seen each other. Both are brought together by low points in their lives. Maggie gets a call that her twin brother attempted suicide. But unbeknownst to everyone, Maggie was contemplating the very same thing when she got the call.

Maggie invites her brother to stay with her and her boyfriend Lance (Luke Wilson) while he sorts himself out, and he accepts.

This time together gives them the opportunity to not only work on the whole brother/sister bonding thing, but more importantly, to examine who they both are now and what they want from life exactly. Meanwhile, Maggie's present and Milo's past refuse not to get involved and throw in a few obstacles along the way.

Although 2011's Bridesmaids may have set up Wiig for comedy projects for life, the canny actress has since shown that she's interest in roles with more depth, as she showed with the warm and sweet The Secret Life of Walter Mittyand now this.

In fact considering that both leads are primarily known for comic roles, this is a film heavily laced with melancholy. Its opening alone is pretty brave for being so sombre. And yet the pair both give a great account of themselves as siblings who, despite being apart, have both been treading water for so many years and are starting to get that sinking feeling.

Director Craig Johnson, on only his second feature – which he's also written – cleverly balances the dark and the bittersweet, to get right under the skin and explore the dysfunctional nature of what should be a close-knit, genial bond.

It's not all doom and gloom however, as Wiig and Hader still manage to bring necessary light touches into proceedings; their rendition of Starship's 'Nothing's Gonna Stop Us Now', for instance, will go down as a cinematic karaoke classic.

It may be unusual for two comedic actors to choose such a dark project to be a part of, but what's more unusual is that they do such an incredible job of it.

This may not be a rib tickler, but with its spiky dialogue and warming performances, it's got a lot of heart.