As always with this game it's quite nuanced on how you see certain things depending on the player.
I'm sitting around 20 Tav's with 95% of them partnered with Astarion mainly Spawn because patch 6 put me off ascended Astarion.(Tav's face)
There is at no point I think he's happy about sharing Tav.
He is always forcing the conversation if you have stage 2 with Gale/Karlach/Wyll/Laezel
"I hear you have chosen a new lover , is this the end for our late night trysts"
Now this to me is a jealousy thing a polyamorous lover frankly won't care too much and his performance here really makes me think he actually cares about the bond.
The replies if you choose against Astarion especially Karlach paraphrased " I heard you sent anothers heart spiralling Astarion I hope he's going to be ok but it's nice to know he actually has a heart"
The Halsin thing comes during a dry spell as someone above mentioned Astarion laughs kind of nervously in my opinion here and uses comedy in reply but as he doesn't want to lose Tav he will agree to it
"Its in someones nature" paraphrased
He will not share you with anyone else Mizora & Harleep have had new additions cementing Spawn is not poly he splits up with you if you bed Mizora.
I personally can not agree to poly stuff with Astarion from the get go [ fragile vampire lover] though I can flirt and tease everyone up till their cut off points and I personally will never force the drow siblings on him as I know his reaction is vacant and things are automatic for his character there.
it looks awkward with AA if you Halsin /AA are wandering around Baldurs Gate as AA stands and watches you and Halsin kiss think he has some random situational banter to trying to remember the video I've seen of such interaction.
So Monogamy is the way I go with him every time.
