Although the Sins are sisters, as far as they can remember, on the whole, they don't look much alike; it is so both physically and about their personalities, which makes sense given how their power shapes their entire beings.
But with Lucien in bed, side by side, Lust, and Envy really do look like sisters; they make the same expressions, act the same way, and even feel the same; they are both lovely and sinful girls.
"So beautiful..." Lucien comments as he caresses Lust's face with one hand and Envy's with the other.
He tenderly touches their sexy mouths, delicate noses, and soft cheeks; his touch carries all the love and affection he has for them, which warms their hearts, a feeling so strong that it transcends their souls and energy bodies.
The Sins are overjoyed by his honest praises; every woman is somehow proud and likes to be appreciated, especially by their lovers, and not even the most masochistic among them can deny that they like it.