supportive dad G who's helped S and been by his side thru his whole transition, helped him get his T, read books and blogs and websites about how to support his trans son. S is very appreciative of it, he thinks at this point his dad might know more about transitioning than he does because of all the research he's done. That's why one day when his dad comes into his room and asks him if he's ready to do a "fertility check", S is confused. He asks what a fertility check is and his dad explains that "well, fertility checks are usually done by fathers with their trans sons. Basically I need to cum inside you every so often to see how easily you can get pregnant. If you don't get pregnant at all over the course of a few weeks with constant unprotected sex then it could mean your T might be harming you". S has never heard of "fertility checks" before from the trans community, but again, his dad has done so much research that he probably knows more than he does. Something feels off about this, but his dad seems so sincere, so kind and caring as always. G seems to sense S's hesitation and adds "I told you I'd help you with anything, this included. /Especially/ this. Fertility checks are very important for your health, and it's safer if it's done by a parent than by a stranger since we share the same DNA so your body will immediately be used it it." It sounds like it makes sense. He seems to know what he's talking about. His dad has always been helpful and supportive, so why should S doubt him? He's probably right about this, and S doesn't want anything bad to happen because he's unaware of some effects caused by his T. “Okay," he eventually agrees, “how do we do it?”. He's never had sex before, and he doesn't know what porn is because his dad restricted his internet access. Plus, he's still young, only recently having turned 19, he hasn't had time to figure out what any of that stuff is. It's up to his dad to teach him what he needs to know. That's what he's done all of s4p's life after all. Guided him through everything, restricted access to certain sites and apps to keep him safe from the cruel outside world, supported him thru his transition and found a safe trans community for him to be in that he accesses through a forum. His dad is in control of everything good in his life, and these "fertility checks" seem like a other good thing his dad is bringing to his life. Eventually, the two strip naked, and G starts touching and stroking S's tdick. "it's growing so nicely" he comments. S has never felt anything like this before, has never really experienced touching himself like this so when his dad slides his fingers into his cunt, he's already so incredibly wet and aroused. "F-fuck, what- what's that feeling? it feels really good, don't- don't stop" he begs as his dad fingers him fast, curling his fingers perfectly. S's moans get louder and louder, his body beginning to shake, his back arching “wh-what- what's this feeling, dad?" he moans before practically screaming, experiencing his first ever orgasm. “You just came, baby," G tells him, fingering him through the orgasm. S cums so hard on his dad's fingers, it's sooo good, and his brain melts when his dad whispers "good boy, I'm so proud of you". G licks his fingers clean, S feels spacey and hazy and he doesn't understand what's happening but he wants more, endlessly more. “Ready for your fertility check?" G asks as he takes his clothes off. Soon enough he's pushing inside of his son, slow and careful and S is almost in tears with how good he feels. “I'm gonna make you cum again, baby boy, just you wait," G promises as he starts roughly fucking his son, wet cunt sucking down his dick so eagerly, tight and perfect like it was made for his dad. And eventually, G cums inside of him, pushing his cum deeper and deeper and deeper inside of his son before slowly pulling out, watching his cum drip from his son's pussy. “How- how often can we do fertility checks?" S asks breathlessly, body trembling and a dopey smile on his face. “As often as you want, son," G smiles, “I'd do anything for you, you know that." His words make S feel so loved and comforted. He couldn't be happier to have such a good dad.