How long should a widower wait to date?

I am dating a widower who's wife died after a 4 year illness. We met 3 months ago and he has not introduced me to his family or friends and has told none of them about me. How long should I wait to broach the subject? I'm thinking we maybe started dating too soon after his loss and I don't want to be the transition person. We met 3 months after she ped away. We really like each other and have tons in common. He is really a great guy. Any suggestions?