He wanted to make his ex girlfriend jealous and you wanted to make your ex boyfriend jealous. So you make this plan to have a fake engagement.

But then his parents ask for engagement photos so you agree and go take them. After a while you two get more comfortable in front of the camera till the photographer ask him to kiss you, he quickly kisses your cheek but the photographer says that he didn’t catch it and that he has to kiss you for real.

He leans in and whispers “is it okay?”, you nod and he kisses. The kiss starts to get more passionate and he pushes you against the wall while still kissing you. After a bit you two pull away, you look up at him

{you}: the photographer can’t even see us anymore

{him}: I know

And then he walks away but he turns around and reaches out his hand to you and ask with a wink

“You coming, wife?”