We can't make assumptions about Grimms when it comes to things like marriage and family based on Nick alone just as we shouldn't make assumptions about hexenbiests based on the four we've seen so far and an extremely biased account found in one of Nick's books. Nick's drawn to the idea of family ever since his world changed at the age of 12. Whether he's right or wrong is besides the point because we've seen at least two examples of a Grimm marrying and having a family (Kelly Burkhardt however short-lived) and another Grimm raising his child to adulthood without issues.
Marie's warning was to Nick but it was about Juliette's well being and she was right. Adalind doesn’t fit that same mould because she's already the "monster" that Marie's alluding to that would cause a kehrseite like Juliette harm. Adalind is a part of this supernatural world, there's no escaping it. And while Juliette could have been hurt by the sudden break up, she could have gone on to live a life of ignorance and find happiness elsewhere and any enemies he made back then would have been from being a cop, which was lightweight compared to the enemies he began to make as a Grimm and wouldn't have dogged her as hard as they did as the kehrseite girlfriend of a Grimm.
I'm not sure about whether Nick deserves happiness or not but there's certainly nothing wrong with wanting to be happy with the life he lives. He was happy for a while with Juliette but then he became a Grimm and things turned a corner, maybe he's found the thing he's been unwittingly looking for without realising it, in the least likely place, in the form of Adalind and Kelly. I certainly think so. If he knew then what he knows now, he would have left Juliette without so much as a thought, for her sake but (without this other worldly threat) could he leave Adalind and Kelly like his aunt had warned him years ago? No, because of Adalind's ability to protect herself and Kelly due to being a hexenbiest almost puts him at ease about her safety some he had even less guarantee with Juliette.
His experience with Juliette has probably left him jaded but not so much that he's grown cold and aloof which is probably what his aunt was trying to do, to give him a crash course in the consequences of being a Grimm (a life of loneliness) without going through the actual pain of loss because he is a Grimm.
Marie's warning was to Nick but it was about Juliette's well being and she was right. Adalind doesn’t fit that same mould because she's already the "monster" that Marie's alluding to that would cause a kehrseite like Juliette harm. Adalind is a part of this supernatural world, there's no escaping it. And while Juliette could have been hurt by the sudden break up, she could have gone on to live a life of ignorance and find happiness elsewhere and any enemies he made back then would have been from being a cop, which was lightweight compared to the enemies he began to make as a Grimm and wouldn't have dogged her as hard as they did as the kehrseite girlfriend of a Grimm.
I'm not sure about whether Nick deserves happiness or not but there's certainly nothing wrong with wanting to be happy with the life he lives. He was happy for a while with Juliette but then he became a Grimm and things turned a corner, maybe he's found the thing he's been unwittingly looking for without realising it, in the least likely place, in the form of Adalind and Kelly. I certainly think so. If he knew then what he knows now, he would have left Juliette without so much as a thought, for her sake but (without this other worldly threat) could he leave Adalind and Kelly like his aunt had warned him years ago? No, because of Adalind's ability to protect herself and Kelly due to being a hexenbiest almost puts him at ease about her safety some he had even less guarantee with Juliette.
His experience with Juliette has probably left him jaded but not so much that he's grown cold and aloof which is probably what his aunt was trying to do, to give him a crash course in the consequences of being a Grimm (a life of loneliness) without going through the actual pain of loss because he is a Grimm.