Headcanon:
Upon realizing that he will most likely never enter a romantic relationship based on who he is, Deceit has become determined to be the best matchmaker/wingsnakeman that he can be for the others in their own romantic crises. He is usually the one pushing Roman to put the work into the flower bouquet he was making for Patton, and even more so encouraging of the creative side to actually give it to him.
He's was the one that actually gave Logan the last little nudge he needed in order to confess in his own dorky way to the side that he had a crush on after months and months of just planning it. He merely told the logical side to just wing it, to not try and plan or control everything, and that it would all be alright. And that if it didn't go okay, then Deceit was waiting right there for him should he need to shed some tears.
It brings him a strange feeling of satisfaction and warmth seeing the others together knowing that he helped them, despite knowing that he'll never have that same love. Because he knows how the others feel about him, he knows that they will never love him in the way that he could possibly love them. And... he's content with that, no matter how much he curls up into his empty bed at night, hugging the long snake pillow to his chest wishing it were an actual person with warmth.
He's really not okay with it, but what is he going to do about it?
It's not like any of the others can actually stand him.