My faith is just not what it once was - How do I become an active Catholic again? - My children won't go to church - My parents won't take me to mass - Why get confirmed? - I would like to become a Catholic
"Children," of course, spans a very wide age range. Children up to about age 15 very often reflect what they have already seen. If attending Mass on the weekend has been sporadic, they may be attempting to take it to the next level (i.e. less rather than more!) as much as testing another rule that growing up invariably entails. Reinforcing that Sunday mass is not a weekly decision point but a non-negotiable family practice is often a good reinforcement. If the resistance is particularly strong (and even if it isn't), having conversations about their reluctance is important, as well as determining whether particular events have given rise to their objections.
Late teenage and early adulthood (16-22 years) may reflect peer pressure or a genuine period of soul searching. In both cases, good, honest, non-judgmental conversation (including your own growing up experiences!) can be helpful. Going to mass even when one is having doubts or "not getting anything out of it" also serves as a good reminder that "staying put" in such times is often the best way to ride through life's challenges.
Adults (and adults with kids of their own) are a different matter. Usually all the conversations are "over." Often a cold silence about church and religion (sometimes lasting years) ensues. The most important reminder is that parents very often recognize the goodness, generosity, commitment, etc. of their children - as does Pope Francis! - here one must let the matter rest in God, do not hesitate to openly practice your faith, continue to pray for them, and let the matter rest peacefully in God's hands (whose love and care continues to guide them).