So far I have discovered the following:
1) Laezel - You don't have to do anything special, just raise her approval and she'll offer you sex. Right in act one. But if you have already started a relationship with Karlach, she will reject you with the reason that she is only interested in "fresh meat".
2) Shadoheart - You must have a high approval and you must not attack the druids in act one. Then you can start a romance (literally right after celebrating the destruction of the goblin camp.)
3) Atararion - You don't have to do anything special, just raise his approval and he'll offer you relationship. Right in act one.
4) Gale - You don't have to do anything special, just raise his approval and you can start relationship. Right in act one.
5) Karlach - You don't have to do anything special, just raise her approval, complete both quests and you can start relationship. But if you're in a relationship with Laezel, you won't get the option to start a relationship. Dump Laezel to get that option.
6) Wyll - No idea. Not even a hint of romance in the first act, despite the maxed approval.
If anyone has other experiences, I will be glad if they share.
Last edited by Edvin Black; 11/08/23 11:07 AM.