Can my follower hold my horse?
Solution 1:
No, horse behaviour is not affected by your followers. Your follower can only hold items and equipment for you.
Horses will always wander off randomly. The only difference in this is that when you do not actually own the horse, it will wander towards its home. But, that said, even when you do own the horse, it might still wander off. You can easily retrieve it by going to a nearby stable, though. This is not the case with stolen horses, which are never flagged as 'yours'.