Parking in your driveway, you and Julia get out of the car. "Because you made me do the shopping, you have to put the groceries away. I'll be in my room, I need some time on the milker." She said, walking inside, "Oh, and you'll have to tell dad why there's no burgers!" She went into the house, thankfully leaving the door open for you.
Sure enough, there was no beef of any kind in the grocery bags. There were also very few dairy products, only some cheese slices and mom's oat milk (not that that really counts as dairy). You suppose that Julia must produce enough for the family, and likely a bit extra to make butter with.
Your younger brother Caden is sat at the kitchen table, working through his physics homework. While you and Julia attend the local university, Caden is still in his senior year of highschool.
You bring in the last bags, as well as your magic binoculars, and set them on the counter. Putting the food in the cabinets and fridge, you ask Caden about his day. He had a history exam that morning that he was feeling confident about, although there were a few kids that didn't quite finish it.
You let him get back to his physics, and sat down in the living room to relax for a bit. The Moo'noculars had somehow gotten into your hands on the way over to the couch.
Scrolling through your phone, you see that in all of your photos, Julia appears as the cow that is milking herself upstairs. Even on his mom's Facebook posts from when they were kids have a thin calf instead of a human girl. The rest of the family is still human, so how... You grab one of the scrapbooks from under the TV. Yep, there's newborn Julia, and she is definitely not fully human.
So your human mother and human father had a half-cow daughter. You decide that thinking too hard about the science of reality altering magic might not be the healthiest thing for your mortal psyche.
You put the scrapbook away and grab the Moo'noculars. You can see Carson punching some numbers into his calculator as your arms raise to your face.
Where once was a skinny young man confidently solving linear acceleration problems, there is now a half-cow woman looking distraught over a trigonometry textbook.
Her breasts and udder are much larger than Julia's, her boobs resting on the table and steadily leaking milk onto her worksheets. She had long, blonde hair on her head, luscious curls spilling down her black and white back. Her face, while still mostly bovine in appearance, have brilliant blue eyes and a plump pair of lips. Two horns curve up from her head as an ear flicks in annoyance.
"Big brother! Can you, like, help me with this? You're like, good at math and stuff. It's asking me for the sin of 30. I didn't know that numbers could be like, naughty or whatever!"
Oh God, the potions! They must have mixed their magic into the Moo'noculars. You just sent your brother from a promising student to a struggling bimbo.
You head over to help her, noting that her udder is also dripping milk into a puddle under her chair. If one of the potions made her a bimbo, the other must have increased her production. You help her through the rest of her homework, using paper towels to prevent her work from getting too soggy.
"Thanks Big Bro! You're like, a total lifesaver!" She jumps up from her chair to hug you, sending her flesh jiggling and droplets of milk flying. You get crushed in a hug for a minute, the pressure enough for her breasts to squirt jets of milk into your shirt. Your clothes now have wet spots of milk all over them...