A/N: I don't think this is the best, but I was given the idea and just had to do it. Spoilers for "Quinceanera."
They had been sitting at the table for nearly ten minuets and Justin was still no closer to knowing why his mother had insisted that they stay home while Alex, Max and their dad all went out for ice cream, Alex grumbling all the while that she was still tired from the heels and couldn't she just stay home. He didn't find it very fair (he liked ice cream) but Theresa had been insistent that the rest go on without her and her eldest, even Jerry's questioning look unable to retrieve an explanation.
Theresa finally looked up from the study of her hands to her son, her eyes cautious. "What did you mean, during the dance?"
"What-uh, what do you mean?"
A breath was taken and eyes shifted slightly. "I was-Alex did a spell. It was ok," she added quickly, "and I don't want your father to know, but she did a spell-"
"Mom, I kn-"
"Let me finish. Please." Again her eyes shifted away, hiding the thoughts and turmoil within before settling back on her son's face. "Alex did some body switching spell, so that I could experience a Quinceanera. It was me you were talking to during the dance."
Justin's thoughts raced, trying to predict exactly what Richard had said to her to have his mother this worried, and exactly how he could repair the damage. She paused long enough to take a breath, preparing and organizing her thoughts for what she would say next. "Now, I know that in the wizarding community it's not as…uncommon for close relatives to start a relationship. Not fifty years ago there were even a few cases of siblings getting married. Although most of those were so that both siblings could keep their powers." A sad, almost bitter smile crossed her face, lingering on thoughts of how two of her children where going to have to loose their natural born gift and one hand absent mindedly reached out to her eldest, planting on his wrist to stroke soothing circles that he suspected where more for her than him.
Justin scrambled back, pulling his hand out from under his mother's and going up in defense as the knowledge of just what she was implying began to sink in. Words stumbled out as he desperately struggled to bring to a halt her dangerous train of thought, "Whoa whoa. I never- Alex and I, we-"
She cut him off with a compassionate look, her hand reaching up to touch his cheek, comforting, motherly, reminding him of sick days and cookies, milk and little boy tears. "It's alright, I wasn't saying that I thought- but," her face contorted in pain, "what you said, calling me 'baby.'" She took a deep breath. "Mi hijo, I love you and Alex, but I don't think… that it would be the best idea for two to..." She made a vague gesture with her free hand, here eyes troubled and full of regret. "I will admit that you two are good together, you bring out the best in each other, but-I grew up in the mortal world, so I don't know how accepted it is in- but your father, he can be a bit closed minded and-. He and I, we wanted to raise you in this culture and so that you'd be prepared, and in the wiz-"
"AlexandIareNOTdating. Grandma kept Max and me from dancing class so we didn't learn how to dance, and so I used the body-switching spell Alex used to change bodies with the dance instructor." She blinked at him, trying to register his hurried confession, while Justin grinned awkwardly at her, eyes begging her to understand and not be upset.
"Oh." She took a deep breath, a touch of embarrassment entering her features before relief swept all other traces of emotion away. "Well that's good." She dropped her hand, fighting back a small smile as she stood from her seat, "Uh, lets not tell your dad about this. I don't think he really needs to know." She hurried off, feeling awkward and uneasy, leaving her eldest son in the same state at the table.
He nodded absently his thoughts a whirl with all that had occurred and the new information he had acquired, planting strange thoughts and images of his baby sister in his mind that would began to take root and grow, causing a far bigger tangle than his mother had ever imagined.
A/N: Well, here it is. A pre-Jalex one-shot, but I already have an idea for a sequel, that will probably also be a one-shot and may even have its own sequel. I am not attempting a chapter fic for this fandom just yet, so that's as close as I get.
Oh, and I see so many stories where the parents are upset about the two of them together, so I wanted to make Theresa accepting, (hence the wizarding world being more ok with sibling relationships than the mortal world, plus I thought that Justin knowing that little fact will make it easier on him to actually be with Alex) she's not happy about it and pretty disappointed, but accepting. I'll explain in a later "chapter" how it is she knows what she knows.