Is this possible to two time 2 characters with high and/or highest virtue? Seems like you get 0% when you ask to be lover when you're already in a relationship. Is there any trick/personnality to boost that?
Possible? Yes. Worth it? Never lol.
First, Highest virtue will never couple with someone if they already have a lover or if the Highest virtue itself already has one. Harems are impossible with them as they're always loyal to one person.
Second, you have a base chance of 20% at High love to become lovers with a High virtue if you already have a lover and at best can be increased to 40% under the right NPC mood and music.
The base chance can go even worse though if both of you have lovers already, which means for you to get a harem of High virtues, you'd have to gamble on alot of 20% success rates most of the time or even worse, like 5-10%.
And on top of that, every time you fail to couple up, the high virtue gains hate towards you, so you may end up in a harem full of angry chicks towards you lol.
It also doesn't help that if you're double timing a high virtue, they're coded to completely ignore you. They will never interact with you, so your harem will feel like a joke.
So in the end, you really shouldn't bother unless you like a challenge and don't mind one sided relationships.