I personally have not experienced that kind of relationship, but I found it believable, largely because Justin was an only child, and he & Lark were together for so many years. Lark understandably would not want to abandon his parents after Justin's death because they were like another set of parents to her and were close ot her own parents. They mourned together. Seven years is a long time to grieve, especially for a woman as young as Lark, but she lost a relationship that was unusually long for a women her age, and Justin was the only boy she ever dated or loved. It was lovely to see that they were present for her wedding to Dante and wanted her to move on with her life & be happy. Hopefully, she will continue to incorporate them in her new life given that Lark is the closest thing to another child they will ever have.