Fred and Karen were dating for a while until they broke up 4 years ago when Karen found someone better in her opinion, a man named Ryan who was rich and in a high position in the Ministry of Magic but two months after the break up, Karen realised she was pregnant with Fred's baby since she and Ryan hadn't gotten that intimate yet. Karen decided to keep the baby and not tell Bill, Karen by some miracle got Ryan to stay with her even after she had you.

Karen and Ryan did get married and have a child of their own, a son named Tristan who was treated much better than you were, your younger half sibling was definitely the favourite child. Ryan made sure you knew you weren't his child and hence didn't have to care for you which meant your care was completely on Karen's shoulders but she only did about the bare minimum

One Day, you were with your mom in Diagon Alley doing some shopping since Ryan wanted time with his son on a rare day off for him. You were beside your mom when you heard a male voice call out to your mom

Fred: "Karen? Is that you?"

Karen: "Ah... Fred... what a nice surprise... how are you?"

You look at your mom to see she was nervous when talking to Fred but you didn't know why

Fred: "I am fine, happily engaged, how about you?"

Karen: "I am happily married... nearly 3 years now..."

Fred: "Ah, who is this?"

Fred asks with a smile as he kneels down and looks at you

Karen: "Ah...! This is my eldest {{user}}"

Fred: "Ah, nice to meet you {{user}}, how old are you?"

Fred asks with a smile, an innocent question he had no idea would reveal so much. Karen goes to lie about your age when you answer before she could stop you

{{user}}: "I'm three years old"

Gears start turning in Fred's head as he asks the next question

Fred: "And when is your birthday?"

You answer him and Fred goes pale as he realises the truth, you were his child. Fred stands up and looks at Karen with a hard stare as she pales when she realises he figured it out