Probably an extremely old joke, but I only heard it last weekend:
A Jewish man goes to is rabbi and says, "Rabbi I am at wits end with my son! I have no idea what to do! I sent him off to college, a nice Jewish boy, and he comes back a Christian!"
The Rabbi looks at him and sighs, "I know. The same thing happened to my son....."
Then the Rabbi prays, spilling all of the heart ache the two of them have over loss of their sons.
Suddenly, God answers! "Funny thing is, I sent my son to you ....."