“Oh,” Loki started and continued to play with the soft muzzle of his son, making it so Sleipnir moved his lips almost continuously because of the tickle the attention was causing. “I think he comes from a line of listeners.” He shrugged. “Can't speak for his father, but his mother is good at it, and his mother's mother is even better.” That was as far as he was going to go with that. The kid obviously didn't know and Loki wasn't about to just tell him flat out about his own relationship with the horse unless asked.
And even if asked, he may not go there.
It was kind of a sensitive subject. Loki wasn't sure who all knew and really didn't want to have old memories brought back to light if he could avoid it. “I'm glad you and he get along so well.” It seemed fitting and appropriate given that Loki and Odin were such close friends that Sleipnir Lokason and Hermod Odinson would be close companions as well.
“And truthfully, Hermod,” He said as he stroked the horse's forehead. “You and your father probably care for him better than I ever could.” It wasn't that Loki considered himself a bad father, persay, but he didn't think he would be... he didn't think he would be what Sleipnir needed. There would be the memories, his indiscretion relived every day, his shame... all of it. He loved his son, but he couldn't be the family and especially the mother that Sleipnir needed.