Truth

twilight looked at spike and sighed softly . Luckily he was asleep .

When he was asking about where he come from , she had lied to him .

Why do you ask ? She was secretly was his mother and he didn't know .

It's best he doesn't know , his father hadn't even contacted her since spike was conceived .

Both spike and his father were dragons and it would make spike's self esteem worse if he knew he was a pony - dragon hybrid .

The only pony's who knew were her parents , Celestia and of course her brother .

Her brother had flipped when she told him she was pregnant . She had to swear up and down that she would not do this again before he calmed down .