A gift is a kind gesture from human to human, the relationship between said humans is irrelevant. Give the gift.

Catalyst, thanks for your reply.
I am very hesitant about this case also b/c of my previous bad experience. Many years ago I gave a gift to the new baby of my workmate. Later he told me that his wife felt very jealous of me. Before that, I ever gave them a gift from my overseas travel......

So this time, I am really afraid that my kind gift may bring unpleasent feeling into his family, his private life... He once explained to me that "everything stays in the therapy room only......" He is a very good professional indeed.

Then if that's the way he prefers it, so be it.

i would just give a small card with the gift that is addressed to both parents, making sure to stress (not awkwardly so) how happy you are for the TWO of them. there is a chance that it could be received wrongly, but i am sure that if you are painstakingly candid with him he will understand your good intentions.

Many thanks for you all. I guess this way will work out. I will do it.
Thanks again. Sincerely!