One Big Happy (2015)

Best friends Lizzy and Luke are like family. As kids, they saw each other's parents go through divorce and have ever since formed an inseparable bond. Now, all grown up and still single, they've decided to start a family of their own, but in a non-traditional way. Lizzy, who is a lesbian, wants to raise a child with Luke by her side. Then one night, Luke falls for Prudence, a free-spirited British girl who's due to go back to England in a matter of days. Then, just as Lizzy discovers that she's actually pregnant, Luke announces that he and Prudence have gotten married and in an instant - a different kind of family is born.