First of all, my condolences for your losses OP.
Yes, I firmly beleive in an afterlife and the survival of the spirit or 'soul' of each individual.
How could I not believe after what I have experienced and seen with my own eyes.
I'm one of those strange types that see spirit people, and communicate and experience their presence, Since 15 years old, I've been aware of the next dimension of existence.
Its just at the corner of our awareness, like looking out the corner of your eye.
Its a higher vibrational dimension, they can visit us, but we cant visit them till we pass over to that plane too.
It doesnt make grief or loss any easier for me, I still keenly feel the loss of their physical presence when someone dies, but it does help me to know they are still around, still able to be near me when I need them, even if I cant always see them, and that I'll join them again someday.
I beleive quantum physics is starting to give us possible answers with multiverse theories and all those dimnsions mentioned in different theories.
As there is a large element of future events given to me in some communications, it shores up my belief that alternate realities, and other dimensions, and time being past, present and future all together is probably on the right track.
We are stuck in 3 dimensions with illusiory linear time here,.. we dont see the bigger picture, but that there IS a bigger picture, and a survival of the individual , I'm sure of.
I also know that love really does know no boundaries of space, or time.