help me find my great great grandpa

hello everyone, I am a teenager from the philippines and I'm very curious about on what happened on my 2x great grandfather and I do need your help, btw heres some context.

1-2 years ago my grandpa told me about my great great grandpa whom was a filipino soldier who fought in WWll and never came back and went missing and supposedly after that my 2x great grandma (or his wife) went out looking for the dude leaving her daughter's and a son, and never came back too.and the only information I have about him is this supposed name "Domingo Caluza" or can be Calusa but I'm sure it's Caluza, anyways, after both parents had gone missing, the five siblings was left hiding and one died from a infection coming from a shrapnel wound.

But anyways there is many holes in this story and most of it is oral passing, my grandfather is alive but he said his mom who passed away 3 years ago never told them about her father or her past. and to clear this up too is I don't know much tbh, I'm not sure if some parts of the story might be altered or fake that's why I'm not very sure.

but what I do know and fact is:

There is 5 siblings

2 in which are alive one is in USA and one is in my Homeland

My grandpa came from novaliches

I am not very close with the 2 great grandmas which is living currently and had never met them.

And I do have some old bills from different Middle Eastern countries and a Mickey Mouse japanese WWll bill.

I had already searched some archives and sites and went deeper on this but I always hit a dead end. And I hope those who are reading this help me research about him and give some tips or clues. thank you that is all.