Jin never really got to know her parents. She only got to hear about them from her Sifu growing up, and even then he only really knew her mother. Jin's Sifu was like a grandfather to her and the closest thing she had to a mom was his Urshifu and of course she cares very deeply about both of them.
Mary had a great relationship with her parents. Her dad was often busy with family business as well as being a gym leader but he would always try to make time for Mary. She would spend a lot of time with her mother. And obviously she took losing them really hard.
But not all of my OCs are parentless! Celeste's folks are alive and well and she's pretty close with them.