Disclaimer: Don't own any of the characters.
Anime: Dragonball Z/GT
Authors Note: I have read some with this situation and have taken inspiration from them. I just hope it isn't a story that has the exact situation.
Trunks remembered the first time he met Pan, she was learning to walk and he and Goten had been roped in to baby-sit, why he hadn't seen her before then was because Gohan had always come to Capsule Corp alone when he wanted something or his mother would go to them. He had never seen a reason to go as he was to occupied training with Goten, he knew what she looked like as his mother had showed him pictures but until then that was it.
The reason for him and Goten to baby-sit was that they had been caught pulling a prank, and babysitting Pan was his mother way of telling him exactly how upset she was. His father hadn't even put up a token of a fight and that told Trunks that he was just as displeased and that he knew just how he felt about babysitting.
Goten had the same opinion and was there for roped in by his mother, and Goten had told him that babysitting Pan was a nightmare especially now that she wanted to walk. What he hadn't counted on was that he would become so attached to her after only one night. In his mind he saw when it happened, she had pulled herself up by the table and again attempted to walk unassisted however this time she was no more then a step away from the table when she lost her balance and started to fall. Unlike the other times she would fall forward or on her behind, this time she was falling backwards and her head was in direct line with the corner end of the table. Goten was in the kitchen getting snacks and he was just getting up from to help him, however the moment he saw the trajectory she was falling in he moved. He caught her just as she was to hit the corner, and snatched her away at that moment Pans eyes met his and something deep within him woke up. Everyone of his senses were at that moment focused on her as every instinct he had screamed at him to make sure she was safe and being as young as he was he had no way to fight the instincts surging through him.
Goten had chosen that moment to walk in with a plate of snacks and when he had gotten to the snacks set down he turned toward Trunks, and he remembered that the moment Goten had spotted Pan in his lap Trunks' instinct screamed MINEand he had growled at Goten. Goten had then stopped up short and proceeded to take a good look at him, before he turned and went over to the phone were he punched in the number to Capsule Corp. Trunks didn't know what Goten had told his mother, but the result of the conversation was that 10 minutes later his parents, Pans parents as well as Gotens parents were at the house. The sight of all the people had him growling deeper and deeper, with the result being that when Gohan asked for his daughter back what he got was a fears snarl with the word "MINE". That had the reaction of setting his father of laughing his ass of, but as Videl got the same reaction when she tried Vegeta had stopped laughing.
His father had then taken a look at his son, and nodded to himself before stepping up to his son. Trunks could still remember his words, but it wasn't so much what he said as the tone and rumble in his voice that got him to let Pan go. "Brat," Vegeta said. "Give her back to her parents; they need her as much as you do. You will however have to prove that your worth to her or she may refuse you." Trunks had looked at his father then and cocked his head as he listened to the unsaid words, before reluctantly handing over the toddler to his father. Who proceeded to give Pan to her mother with a smirk on his face.
They had left not long after and though he would both see her and baby-sit her several times later he would by then have control over that part of his instincts, at least until she was grown up.
Smirking Trunks looked up as his mate walked in, their courtship had been just as exited as their bonding if not more so, however that was a though for a different time.