I don't personally believe in life after death, or anything like that. However, you could try speaking to your twin flame, or try writing them letters to them and stuff like that. It is an entirely one sided relationship, as even if there is an afterlife and they can hear and understand your attempts at communication, they really don't have much of a way to reply. It may help you feel better though.

It is possible to feel connections with people who have died, and see them in dreams or feel their 'presence' while awake. Religious or spiritual people may say they are really there with you. I don't believe that, but I don't discount those feelings either. The memories, and love you had for your twin flame is a real thing. That is where they live now, in your memories and in your heart. As long as you remember them, and think of them, there is a part of them still with you. As you said, your lives blurred into one, and so in some ways you are one and as long as you are alive they are alive in a way, as they left a large and permanent mark on who you are.