When I was young, the constant message was "Stick with your own. Marriage is hard enough without adding difficulty to it." So, we dated within our denomination and discovered there were a multitude of understandings within our "commonality." My children have grown up and live in a different world. And I am delighted.
Two of the three married siblings wed individuals who embraced a denomination other than ours. The other one married a young man who was raised in our faith but has become an agnostic, his words not mine.
All three, actually all six, are wonderfully religious. Only one regularly attends church and participates in its functions. The others follow their own road of spirituality. I am in no way dismayed by the denominational differences. However, I am conscious of times when life struggles might well be minimalized, perhaps normalized, if they were part of a faith community. This is not an observation I share with them. I choose to let them discover this for themselves, if it is at all meaningful to them.
As they age, they grow in wisdom and grace. One son-in-law has decided to embrace the faith in which I was reared. He did so, not from being urged, but from the example of holiness he saw in my husband as well as in the pastor of their local church.
My relationship with all my children remains an ongoing entry into mystery. It is, however, made a more tangible journey with the ones who have similar contact points. It is easier to speak of God and church with the ones who are at ease with that kind of conversation. Denomination has little to do with it.