Disclaimer: I do not own any HP characters. This takes place after Chamber of Secrets and before Prisoner of Azakaban. Enjoy
"Lily, you need to tell Snape about Harry and Hermione." James told her as she held Harry, thinking about how much he resembled Snape, except for his eyes and about her daughter who she gave to the Grangers. "James, I can't. You know that Severus is spying for You know who and it's luck that he hasn't been forced to take the Dark Mark. James, please understand that Severus can't know that Harry and Hermione are his children, because if he did, I hate to think what You know who might do. Please, James." Lily replied to her husband. "For you, Lily. But once You know who is vanquished, Snape must know." James replied as he looked down at Harry. "I know, James. But until than, I will place a glamour charm so Harry looks like you up until his thirteenth birthday like I did with Hermione." Lily told him. "Lily, how do you plan on telling Snape, Harry and Hermione this if we end up dead before than?" James asked her.
Lily looked at her husband, "I have already written three letters that are spelled to appear to them on Harry's and Hermione's thirteenth birthday." James looked back and sighed, "I hope to Merlin that Snape will understand your reason for this." He told her. "James, I know Severus and he will. Once he reads the letter I have written." Lily said to him as she rocked Harry to sleep. "Does your sister know?" James asked. "Yes, Tuney knows and I have made her promise me that if something were to happen to us, that she cannot tell Sev and that she must do her best to protect Harry from her husband. You met him, James." Lily replied. "I know and I don't like him one bit. But can you trust her, after all she said to you?" James asked her, worry evident in his voice. "Yes, I do. While she may not like magic much, we're still sisters." Lily told him as she put Harry in his crib and tucked him. "If you say so, Lil." James replied. "I do. Let's go to bed." She said to him as she turned off the light and left the room. James soon followed her, wondering if he'll be able to keep this not just from Snape, but also from Sirius. 'I'll worry later' He thought to himself as he followed Lily to bed for the night.