My [24F] ex [22M] died unexpectedly. How do I grieve while in a relationship?

This week I found out my [24F] ex [22M] took something that was laced and was declared brain dead and I?m expecting he?ll be taken off life support soon. We broke up three years ago, haven?t spoken in over a year, the relationship was very much over, but I?m still heartbroken about it. We ended on good terms and he was so young and he deserved so much better. My boyfriend [28M] and I have been together for a year, and he?s been very supportive since I found out, but I feel weird about being upset and grieving an ex while in a new relationship. If anyone has been in a similar situation, how did you handle it?
tl;dr- ex died, i?m big sad, what do i do


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