Firstly, my condolences on the loss of a beloved pet.
Secondly, no it's not unusual to sense a deceased pet being around. It hurts like hell to miss them, but it's comforting to know that they miss you as well.
After I lost my Puppy (she was 13+, but you couldn't tell HER that! Didn't act her age until into her last months), there were several times at night, when I could feel her jump on the bed. There was a distinctive way that she laid down (more of a collapse), and I knew that feeling all too well. It let me know that she was o.k.
Every now and then, she'll appear in a dream, and it's cool, having a chance to spend time with her again. Dreams are more interesting, once you realize you're in a dream while you're having it.
Being someone that has lived in 'haunted' houses in various places, has two spirits that have followed me from two apartments, and into my home (where they currently reside), and talked to my Dad in a dream after he passed, this kind of stuff is second nature to me.
In a dream, Dad and I are driving down a road in his old car. I turn to him and say, realizing, "Wait a minute, you're dead". He looked back at me, smiled, and said, "You're right". After that moment, I knew that I was going to be all right. Been 13 years since his passing, but he still pops in every once in awhile.
Sometimes, talking to your deceased animal will help. Just kindly ask him to stop scaring the young one. That'll probably do the trick.