All the more reason for Catholics to ensure friends and family stay faithful. Someone who is raised Catholic and willingly departs from the Church and does not repent is not in a state of grace upon death. So perhaps there is hope for Purgatory, in which case prayers and masses will be blessings for his soul.
As difficult as it may be to hear, @Aulef is correct. We do not do ourselves, our family, or our friends any favors by trying to wish someone into heaven after they die. We must guide then during their time on earth.
That all being said, I will pray for your brother in law.