I don't have a Christian name and not do any of my family. That said ....
My father and mother insisted we called them Mama and Dada when we were kids. I hated this and found it embarrassing as I grew older. Then my father said he was happy being called his first name (Heinz) and my mother eventually followed suit with her own name ( Juanita). Once we had our own children, their first grandchildren, my father refused to be Grandpa or granddad and asked for Heinz ( negotiated to Papa Heiss by our children) and Juanita became Mamanita.
Now my grandson, of his own volition, calls his mum and Dad by their first names, from a small child. He sussed that he'd be answered faster that way, having observed and drawn his own conclusions!
He still calls us Grandma and Grandpa though.