Simba and Mufasa always had a loving Father and Son Relationship.
It is shown in a flash back from Mufasa that Daddy was Simba's first word. Simba seems to have the closest Father-son Relationship in the whole series. They often spend nights together under the stars, and have morning lessons about Simba's Kingly duties. Simba often confides in Mufasa when he has a problem or is scared about something, since he finds his Dad to be very wise and comforting. Simba has respect for his Father and tries to do his best to impress and be just like him, but it often backfires. Simba seems closer with his Father rather than his mother, since they have more interaction and understand each other more.