As Halsin and Shadowheart fall deeper for each other, he takes the lead as the MC running the party. His team rarely includes you so most of the game is sitting at camp with Gale and the pets and Withers asking about your relationship.
Cut scenes with them sharing a tent, laughing and playing all through the night while you try to sleep next to "gassy Gale".
The game proceeds this way where you get to hear about all the things they're doing in the world until they solve the crisis and live together in marital bliss, hiring you on as a caretaker (since you weren't involved much, you aren't entitled to much of the spoils)

"I'm.... I'm really happy for you two" you manage to get out with a weak smile at their wedding
They smile politely and look at eachother
"Oh, Astarion! Ahh, please do excuse us" Shadowheart says, leading Halsin away as you try to look casual standing alone by yourself.