If your grandfather was Doming, of Arcega's Department Store, he was my "Primo" or friend, and I knew him personally and professionally between 1945 and 1962. Arcega's bought stationery and office supplies wholesale from us, De La Ysla & Arcega Bros. in Manila, right after the war. But I became more closely acquainted with Primo, when Arcega's supplied my company, Ysmael Steel Mfg. Co., where I was working as Asst. Advertising Manager.
As far as Primo and I could determine, we did not share family tree directly, as his family was from Cavite or Batangas (?) and mine was from Tarlac and Pampanga. I did grow up in Caloocan, Manila, and lived in Quezon City before I left the Philippines for Canada.
I've been trying to develop a working genealogy, and if you're doing the same, I hope the above information help, for openers. We could exchange more details, if you think these could be useful.