How can you say no?

You can't deny the attraction any longer. Like a tension you never knew was there, there's been a growing need for this in you, and apparently in Kayla too. Were all those feelings-- the anger, the resentment-- just plain envy? Have you really spent all this time simply wanting what Frank had?
You pull her sweater over her head. "Who needs a couch?" Tara laughs. You pull her off the desk, hiking up her skirt to grab and remove her panties.
"Oh baby..." Kayla is breathing heavily now. "You're so sexy..." she runs fingers through your hair, and you put her back up on the edge of the desk, sitting down in your chair to dine on her neatly trimmed snatch.
"Mmmmmff.....damn....that's...." she grips your head as you explore this new territory, licking and sucking on her clit as you probe her slit with a crooked finger. She's tasty: a little tangier than you're used to, but not unpleasant at all. One finger becomes two, expertly seeking out that magical internal button.
"Oh....OH....James....It's been....so long...." she's quickly becoming a sticky mess.
"Not since...?" you leave the question hanging in the air as you go back to work.
"Mmmmn....no...couldn't ever....seem to go through with it..." she pulls your head back to look at you. "I guess... I always knew the one I really wanted was the one I couldn't have..." The look in her eyes tells you that she isn't kidding. Wow. Who would have thought? Had she felt this way when your dad was still alive? This is a fleeting thought, and can't compete with her eyes.
You stand up, letting your shorts drop and your cock spring out. She looks at it with desire.
"It's...perfect..." she leans up to stroke it. You sit back down into the chair, and she pops off the desk, stripping off her bra to reveal her perfectly round titties. She slobbers on your cock with gusto, and then gives you a heavenly titty fuck.
"You're beautiful, Kayla." you stroke her hair. "I've always known it, but I guess I never really saw it until today. Come here." You pull her up into your lap, taking a moment to slide your cock up into that pussy.
Kayla whimpers and moans so cutely. "Oh....mmm....that's filling me right up, baby." She kisses you passionately as she bounces slowly on your dick. You run your hands up her back, return her kiss with passion of your own.
"Oh...that's some really good dick, James. You don't know how much I've needed your dick in me." Her words only fuel your illicit desire. No time for regrets at the moment. That could be the Sinclair motto, you realize.
She pops off your dick to spin around, showing you her luscious ass. "Give it to me." she slides back onto your dick, and begins to ride with true abandon.

"Oh....fuck....Kayla...." you grab her tits and squeeze as she grinds and bobs on your cock. Your balls are tightening up. "Kayla I'm gonna..."
"Go ahead... you can cum in me, James. I insist..." she leans back, and you hammer upwards as she bounces, spearing her g-spot with precision.
"Oh yeah! Oh Yeah! That's it baby!! I'm ready for your cum!" she devolves into incoherent moaning and screaming as her orgasm peaks, and you pull her all the way to the hilt and shoot deep into her pussy.
After a few minutes spent in afterglow, with her sitting in your lap, kissing and catching your collective breath, you speak up.
"So...that was a long time coming, I guess, huh?"
"Yeah. Sometimes you just can't lie to yourself about what you really want anymore."
"It's not weird?" You lace your fingers with hers as she rests against your shoulder. "I mean...you were basically dad's mistress."
Kayla grunts. "A part of me will always love Frank, James. But... as time has passed, I've started to realize that he never really felt the same. I was a good fuck, and a piece of eye candy. He never mistreated me or anything, but... I know now that he never would have loved me the way I loved him."
"I can't...I mean..I can't promise..." she suddenly looks at you.
"James..I don't want any promises. I know you aren't free. This was... amazing. And exactly what I've been needing, but I don't want to cause problems. This is a one-time thing, agreed?" The look in her eyes... how in the hell are either of you going to be able to make that happen? You've never been more snugly captured in your life. But you nod, anyway.
"Shit... James. You should get home. Thank you...for the loan." She kisses you with love and passion. "And for the first good dicking in two years." She climbs off, and you are scared by the amount of regret you feel about the loss of her body.

You spent too much time at the shop getting your dick wet, and you hit unexpected traffic on the drive back. You curse as you also realize you never fully gassed up the Jav, and so you waste more time trying to maneuver into a crowded gas station.

The result is that you pull onto your street to see the travelers have already arrived. Everyone is on the lawn, greeting and hugging each other. God damn it. You had wanted to be home when they got here.