What i know usually is 3 months after.
Means if your wedding is in December 2018, then cannot attend wedding till March 2019.

But then again, different families different belief different practice.

So it depends on your belief.
Since you are attending friend's wedding and not your wife's family side, your wife's family belief shall not impact you.

This post has been edited by MiLKTea: Mar 15 2018, 10:06 AM