A lover that focused on the partner reaching peak is quite the treat.

Phoebe had been quite keen on ensuring her brother not only could identify each weapon and gem by sight but the history of each and its role on the battlefield as well as the detailed lore surrounding the Shadowbolts themselves despite his having no real interest in the subject. But that didn't mean that each of her lessons wasn't enjoyable when seeing her face light up with joy upon passing one of her 'exams'.
The sex afterwards was great too, when circumstances allowed and unfriendly ears weren't listening.

Hopefully such circumstances happened often enough.

“Are you wearing… vanilla?” Charon felt a wave of anticipation grip his very core as she smiled suggestively back at him and gave her pinnae a wiggle.
“About half a bottle of extract… all over my ears.”

Her mother would be proud! (She tried something similar in the prequel.)

“EeEeEeEeEeEeEeEeEeEeEeEEEEEEE~! She screeched out as she alternated between giggling and moaning, screeching and laughing, as if the insanity of pure passion Charon was experiencing had infected her as well. She tried to form words with her mouth but all that came out were reduced to the savage disjoined syllables of a prehistoric cave-bat pony.

I wonder how many had heard this...

“Are… you okay, Pheebs?”
“Eeeeeeee…” Phoebe just managed. She looked up lazily at her brother before her eyes found focus and she looked down at her sheet with a gasp. As she’d predicted, it was soaked clean through; Charon could see her blue, puffy entrance, winking aggressively, as clearly as if the sheet were an open window.

Sounds like a clear yes to me.

“What was I supposed to do, Charon? Say ‘sorry, Mom, I’m already in love with my brother!’”

: "I don't see anything wrong with that!"

He climbed out of bed, circling her as she stood at attention. “There’s only one thing I’d fix… Your wings are a bit dry from your last bath. How about I oil those up for you?”
“Actual preening? Aw! You’re a hopeless romantic, Charon!”

Not that anyone is complaining...

“Whew! Sorry about that. Didn’t mean to completely empty you out…”
“You liar!” She cooed back to him before pouncing him in an affectional tackle. “Now open your mouth and let me have some of that!”

Listen to her!

“Please, stop! You’re going to make me waste my load!” His voice nearly as high-pitched as her sisters had been and fighting off the uncontrollable urge to laugh that accompanied the sound of eager slurping in his ear, his knees wobbled from the intense stimulation, fighting a valiant but slowly losing battle to hold off his orgasm.

Very good argument.
But even if he lost it, she would merely convince him to make more for her!